BMW 330i 325i E46 Using Fuel Trims To Diagnose Engine Problems P0171 P0174

[@cxoakes]

You have a gift my friend. You have become an invaluable resource for many of us.

[@DS-ss396]

I'm pretty sure he took a Automotive Technician course.

[@jamaljabari4577]

I guess im asking randomly but does anybody know a method to log back into an Instagram account? I was stupid forgot my password. I would love any help you can offer me

[@leonelkarter3826]

@Jamal Jabari Instablaster :)

[@jamaljabari4577]

@Leonel Karter thanks for your reply. I got to the site through google and Im in the hacking process atm. Looks like it's gonna take a while so I will get back to you later when my account password hopefully is recovered.

[@jamaljabari4577]

@Leonel Karter It worked and I now got access to my account again. I am so happy:D Thanks so much, you really help me out :D

[@Jeffleezy]

I've watched hours of other fuel trim videos on KZbin which left me super puzzled. Yet you've managed to fully elucidate fuel trims to me in 18 min. Thank you so much. You've done so much for me, my E46, and my wallet. Words can't even convey my gratitude.

[@lp2565]

Started working on my E46 330Cica recently, when I retired. Your videos have become my source for repair information on the M54. Hope you are doing well!

[@carlos92161]

Man I don’t know how to thanks for all your knowledge shear with us personally I really appreciate it

[@elvinnovruzov5775]

man, you bring so much happiness to the life of e46 owners

[@terrybuxton8543]

Hey great video's, I've been chasing high LTFT for a while. I"ve replaced pre-cat O2 sensors, CCV system, fuel pump, fuel filter, both intake boots, IAC boot, rebuilt the DISA valve, replaced the Brake master cylinder vacuum hose, the tee that connects to the boot, checked all vacuum lines. I've cleaned the MAF sensor. The STFT will hanging around 0, but the LTFT still reads around 11. I finally replaced the MAF sensor and It corrected the problem. After about a 30 min drive , STFT was reading around 2 and long LTFT fell to 0. My car is an 06 325ci vert with 112k miles. So it seems that the old MAF was not correctly reading the amount of air entering the engine, so it looked like a vacuum leak / lean condition but in accuality it was a faulty MAF sensor not measuring the correct amount of air entering the engine. I guess the most puzzling thing was the car ran and idled good and smooth.

[@Omardottcom]

I’m having the same damn problem.... my car was reading around 12% positive fuel trim on both banks. Then it got a cylinder misfire in cylinder 3. I did a smoke test at home and found the intake Manifold Gasket gasket was leaking... it replaced it. Stopped leaking. Still the same trims. Found a couple spot leaking. Got some hose clamps and stop the leaks. Did smoke test again, no leaks. Still same trims. Repalced the fuel pump and filter with built in regulator... trims dropped from 12% to 9-10%. O2 sensors seems to be reading correctly as well as the MAF sensor. It reals about 14-19 kg/hr. Not sure if it’s lying. This is so frustrating.

[@Sakanatuga]

@@Omardottcom you solved your problem? i have the same :(

[@Sakanatuga]

@@Omardottcom you solved your problem? i have the same :(

[@Omardottcom]

Andre P I haven’t technical solved the problem but made it good enough to pass inspection. As you know, I change my intake manifold gasket which has a leak. I put hose clamps on all the hoses. I changed the fuel pump and filter. I had a little leak at an o ring on one of the ccv connection threat was leaking so I replaced the o ring and stopped the leak. I changed the oil filler cap which didn’t really have a leak but smoke would come out of it if the pressure was high enough when using the smoke tester I made. I checked the injector o rings and they seemed good. Some how my trims dropped to around 8% and have stayed there so far. The service engine light went away and I was able to get it inspected and pass. But the trims are still too high. When doing the smoke test smoke doesn’t come out of anywhere. I don’t know what else to do.

[@kalas1988]

I have M54B30 with strange fuel trims. I checked fuel filter which was 12 years old. I still cant believe it! but this solved my trims on both banks! Amazing!

[@timdavis937]

This was the easiest video I’ve watched explaining the way most modern fuel injected computer based cars run. I am so grateful that you are so willing to share your knowledge! This will help me on much more than my e46, I can use this knowledge troubleshooting my other vehicles as well.

[@Mikeeey01NZL]

finally clarity, thank you so much for explaining this, best explanation ive seen yet.

[@biflos7]

wow, I've never seen better explanation of fuel trims than yours, big thanks!

[@JoshuaBerg]

I knew nothing of this, but within minutes totally get it from your excellent explanation.

[@jasondizon5215]

watched tons of lean code videos, this one is made me understand how those fuel trims work. thank you!

[@johnherbert5919]

This is the best explaination of fuel trim I have seen, thankyou.

[@titanf30]

This video just may be what I needed. I've been looking for solutions and this may be the ticket to fixing my car! Kudos to you.

[@scottmurray18]

your very talented not only with motor mechanics but you explain things very clearly and easily. you have been a huge help, thank you very much sir.

[@whichdoctor4858]

Thanks 50’s Kid! Will take a look tomorrow to see my trims from those lean codes.

[@Dondog15]

Hello everyone, I have an 02 325ci and got some codes. Currently swapped my maf sensor, last week swapped the ccv system and valve gasket. Realized I have a small oil leak under the oil pan gasket as well. I am still getting codes p0171, p0183 and p0185. I hope to figure this out on my own but just want to say thank you so much for these treasure videos.

[@Dondog15]

Another thing, when I drive around 2000-2500 rpms,my idle drops very quickly then shoots back up. Only when I’m constant on my pedal this happens. I’ve stopped driving it to figure out the problem.

[@maxsmith2320]

hi , i am a bit late 4 years but this is the best tutorial on fuel trims.

[@bobcampbell4263]

50sKid Hi, so I worked out the 28B8 problem. Took off the exhaust solenoid again and felt the piston that the solenoid drives... it was frozen. Carefully removed, cleaned the piston and cylinder area, reinstalled... ran perfect, no more codes.Thanks Bob Campbell

[@50sKid]

+bob campbell Aha, very nice job. I will note that fix for this error should it ever come up!

[@WV591]

my P0171 on sentra is impossible to fix. 4 months of testing replacing parts and still problem.only on youtube is always cracked intake boot....wish you had graphed the MAF sensor when you created that vacum leak.good film TU.

[@josephcarter7]

Thanks a bunch been tracking my P0171 P0174 issues found found the trim levels to be 27% sounds like a massive vacuum leak thanks again!

[@TheOwlGuy777]

+josephcarter7 If you are over 100,000 miles with Bosch O2 sensors, replace them. It solved my 171/174 codes.

[@50sKid]

+Robert Tison Replacing O2 sensors doesn't solve massive vacuum leaks. Please don't advise someone to spend $100 on parts they may not need when what they really need to do is look for the source of their leak and replace THOSE parts.

[@TheOwlGuy777]

It's $200 on parts and when you have replaced another $150 in needless parts that solve nothing, it gets expensive quick. My oil separator was fine, the hoses were fine and mine has an electric EGR. My O2 sensors were erratic and causing the codes that indicated a vacuum leak.

[@50sKid]

These cars don't have an EGR system of any kind.

[@TheOwlGuy777]

The electric air pump at the exhaust that has the vacuum valve. Mine has no vacuum valve. It's electrically controlled.

[@TheOwlGuy777]

My fuel trims were erratic with the scan tool. I had no vacuum leaks. I had 0171/0174 codes. I replaced both upstream O2 sensors and it is now completely stable. Bosch O2 sensors only have a 100,000 mile life span I found out.

[@50sKid]

+Robert Tison Both oxygen sensors died at the same time? Statistically, I think you just won the lottery, lol.

[@1979pjmfni]

Thank you man, I solved my problem thanks to you and now my car passed the smog test.. You really know a lot!!!

[@50sKid]

Nice job 👍

[@TomStewart-g3q]

Great video you help us all a lot, I don’t know if you’ve had this vacuum leak, took me a while to find it, it was underneath the bolt holes on the rocker cover, very very small cracks underneath the rubber seals, just one to look out for boys & girls👍

[@toto29620]

Hi, great bravo from France ! You speak very clearly and your are very good at explaining stuff, your video have helped me a lot with my E46. Keep up the good work!

[@50sKid]

Thanks!

[@andyridley2236]

Very good video easy to understand i am no longer puzzled about fuel trims.

[@Meatpipeify]

How would you go about diagnosing if the long term fuel trim is high? I have an '03 Z4 that had a DISA leak and torn intake elbow, and its long term fuel trims are 11%. Assuming if it's all fixed the short term fuel trims would be -11%, indicating the short and long term would cancel out? Or should I reset the DME and start from scratch? Thank you!!

[@mashzilla]

Hi your content has been amazing! So I used the fuel trim to help identify my p0174 p0171 codes but after fixing the vacuum leaks I continue to have the codes. Now that all the vacuum leaks are fixed I notice the fuel trim goes 27.3% at idle and holding at 2500rpm it drops to zero then within 5-10 seconds climbs back to 27.3% on the STFT. Here's a list of the work done. Cleaned the MAF, changed the intake boots, all the vacuum lines, intake manifold gasket, new spark plugs, ccv replacement, icv grommet, throttle body grommet, new fuel filter and fuel pump was replaced last year. I appreciate any help thanks!

[@BigWakeGuy]

What was the problem? My STFT also reads 27.344% very regularly which is such an odd number to stay at for both of them

[@robeaton2191]

Did you find a solution to this? Mine is exactly the same. Thanks

[@mashzilla]

@@robeaton2191 lol I sold the car was my solution.

[@robeaton2191]

@@mashzilla looks like i bought it lol

[@MrHaaaj]

Lol I'm having same problem with 27.3% on STFT. Did you find out the problem?

[@Eugen-2u]

good job man . thanks for explaining all that stuff to me.just got 330 ci and everything needs to be changed .

[@JA_Everything]

Great Video (As Always), You do have the art to deliver information in a good and comprehensive way people can understand. Thank you. Can't wait to see the video on how to replace that fuel regulator.On another note, Can you make a video dedicated to the Vehicle interphase and the software you use?I've been meaning to acquire one of each but not convinced on which way to go on terms of hardware and software.Take Care and keep up the GREAT work!

[@carolynbedard]

Is there a reason your video has the settings so I can't save it in my play list? It would be nice to view again but the lack of this setting makes it hard for me to find again.

[@porsche1959]

Thank you. I'm still getting to grips with the software but mine was #2. Dirty MAF. Replaced and 200 miles so far so good 🙂

[@danytrabolsy]

@50sKid, i have a problem with my 2002 330ci, sometimes i have lean codes thrown at bank 1 and 2 other times MAF code. at cold start the car hesitates and sometimes stalls but very responsive and alot of power, once it reaches operating temperature no more stalling but most of the time it has no power like accelerating in 4th gear and other times it jumps and awakens then back to no power, above 4000 rpm the car runs fine. reading the fuel trims, at idle everything is close to 0 (fluctuates between -2 and 2) but once i put a little acceleration the trims are flying (up to 18 to 22% inpa lambdaintegrator bank 1 & 2) the things i've done : replaced O2 sensors (maintenance) replaced fuel filter and fuel pump replaced CCV, oil filter housing gasket, valve cover gasket checked the fuel pressure both at idle and throttle it's stable at 3.2/3.3 bar any ideas where i should be looking next ? i eliminated the vacuum leak since at idle the trims are normal could it be the MAF ? cleaned it (with no change), if the MAF is dead would the fuel trims be normal at idle? thanks.

[@50sKid]

Your fuel pressure actually sounds low. It should be 3.5 bar/50psi. What brand gauge did you use for that test? Anyway, if the MAF was dead your car would either not run or the computer would recognize that and substitute a value for the MAF reading and that value would most likely be higher than normal and you'd see that reflected in the fuel trims. But your MAF could be out of calibration and causing the problem. Anyway, the most important thing I want to explain is to not use INPA fuel trims to diagnose things. The INPA "trims" are not the same thing as the OBD2 short and long term fuel trims. They mean different things and they can't be used to diagnose problems the way I explain in this video. You need to get an OBD2 code reader that supports live data and you need to look at short and long term fuel trims on banks 1 and 2. Now, once you do that and IF you still have the same behavior (normal at idle, higher at speed), the possible causes for the problem you are describing are: bad O2 sensors, insufficient fuel delivery, or bad MAF. So first confirm that your fuel pressure really is low, and especially confirm that it doesn't drop lower at speed, and if not, replace the MAF with an OEM Siemens one.

[@danytrabolsy]

Thanks for your answer, i'm back with more data. the gauge i'm using is not very good, i ordered it on the net and it's like a tire gauge so i ordered another one waiting for it. in the mean while i got a new MAF VDO and tested it but changed nothing so i returned it back. and i got my self an OBII scanner and here are the results after resetting the fuel trims : at idle the short term fuel trims are - 4 to -5 at 3000 rpm the sft are at 19/21 then at 4000rpm i got 10/9, all in closed loop. the catalyst, secondary air system, oxygen sensor, and oxygen sensor heater status says : not complete. i measured the sensor 2 short fuel trims (post cata.) and they both had 99.2% not sure if that means anything, also measured the voltage that drops when accelerating. i'm waiting for the new fuel pressure gauge to get an accurate result, but i think i eliminated the MAF, but i don't know where to go from there.

[@janvandenbroeke2628]

Very informative I have exactly these fuel trim diagnostic codes and will now follow your instructions thanks a lot ..

[@freemanmiracle7975]

Why you need to take out the fuse and let the ignition die? Did you plug the fuse back when using the fuel pressure gauge? Please explain. Thank you

[@KyleMontanaro]

Hello mate, brilliant videos, thanks for all the explanations and example. I've got a 2001, 316Ti (the liftback ones) with the N42 engine (I know, 1.8l, small, blah blah...) and I've been using these bluetooth OBD2 reader and the Torque app on my phone, which has already helped me out a few times. Recently after every (relatively) cold start, the acceleration of the car suffers a lot and it makes a muffled noise as if it's overfuelling or chocked. This continues throughout the warmup and usually doesn't go away on its own until i turn off the engine and switch it back on, at which point it works as if nothing happened. After seeing this video, I've configured the app to read short and long term fuel trims on all sensors and what I've noticed is that after a cold start, the short term fuel trim goes crazy and fluctuates from around +8 to -8 all the time even once the engine warmed up, but after shutting it down and restarting it, it all smooths out nicely. Any idea of what might be going on please?

[@manujadesilva22]

I don't understand why a large, consistent drop in the fuel trim under higher RPMs denotes a vacuum leak. Could you explain this further ? Thanks for the great video

[@BigWakeGuy]

Think of it as a contaminate almost. When you increase rpm, you get more air and are basically diluting the extra air “contaminate” caused by the vacuum leak.

[@uyenngo4170]

Hi Jason, Thank you for informative video. I watched both of yours, and try to trouble shoot my P0174 code, which recently pop up (don't have P0171) Engine idles and car driven normal on both city and highway P0174 came back after reset, while driving but not after engine starts , not at traffic light. Here some additional info... -New Valve cover gasket (less than 3K) -New fuel pump (less than 15k) -New DISA (less than 18K) -New fuel regulator (less than 50K) -New CCV valve (less than 50K) -MAF is original, cleaned few times I will your technique to determine to see it is a Vacuum leak or lack of fuel? Again, thank for video. Please let me know your thoughts

[@blainegabbertgabonemhofgoa6602]

if it's just 174 and not 171 it could be o2 sensor. check o2 sensor voltages to see if that's the problem

[@Heethoofd40]

Thanks for all the great video’s I understanding fuel trims now

[@JMUDoc]

I've just replaced my fuel pump regulator to get rid of negative trims, but the trims are now biased positive - will they come back to normal with a bit of driving, or do I need to do a reset? If the latter, how would I do it? All I've got is an OBD code reader...

[@TedSchoenling]

First, Love the videos, thanks! I've watched most of them even though I don't have most of the issues you are having, it is good to know these things and you cover them well. So I'm going nuts here. My fuel trims are 20+ when in Open Loop, with a misfire on various cylinders. Once the ECU transitions to closed loop (warmed up) the misfire goes away and idle smooths out (not perfect, but pretty darn close). Fuel trims drop to around 6. I have pending lean codes as well as misfires (random) on 5 of 6 pots. When RPM rises fuel trim approaches zero regardless of Open or Closed loop. So I'm sure I have a vacuum leak, but why would things get better when the car warms up? I've replaced the DISA O-Ring, secondary air pump hose, upper intake hose (lower is on the way) and checked other issues. I don't suspect CCV but that my be wishful thinking (no smoke, no excessive oil consumption, vacuum on oil fill cap not excessive. arrggghhh

[@TedSchoenling]

I also cleaned my MAF.

[@50sKid]

Ted Schoenling have you visually checked the CCV tubes themselves? You can see the lower one from under the car. If you unplug the maf while the car is running and plug it back in, that should reset all the long term learned trims and get you back to a baseline where the car will relearn so try that and see where you are.

[@TedSchoenling]

I haven't yet done that. but I find it odd that everything would go normal with such a large vacuum leak. When it is really cold. When I spray carb cleaner on the lower intake boot the idle improves (when cold) so I know that may be an issue, I'll have to get the car in the air to see the pipe, and with snow on the ground not something I'm looking forward to, even in a garage.

[@50sKid]

Ted Schoenling yeah so if you sprayed carb cleaner on your intake boot, you found your leak. Remove it and examine closely

[@TedSchoenling]

I'll do that when I get the new one.. the (not so nice) guy who put this boot on put the clamp on so that it is facing down and away, I'm afraid I'll have to rip it apart to get it off. I did get the car up in the air, the 0-ring on the dipstick may be suspect, but I do have vacuum at the top of the dipstick so I'm not sure about that. I also have an oil leak at the oil pump filter gasket, which was a known issue, but it is starting to make a mess... that will be the next job.

[@reytorres9221]

My LTFT is -4.7. What is the optimal value I need to watch for?

[@50sKid]

+Rey Torres 0 is the normal value. Sounds like you may have a fuel over-delivery issue. Have your fuel pressure checked. It should be 50psi (I gave an incorrect value in the video).

[@reytorres9221]

+50sKid , Hi there. I have not check the fuel pressure yet. A year ago I replaced my fuel filter, fuel pump, and fuel level sending sensor. So If I have issue with fuel pressure regulator, my fuel filter is bad? The fuel filter has regulator in it. So where do I start? Thanks, Rey.

[@reytorres9221]

BTW today my LTFT is -3.1 but while driving about 15 minutes its up to -3.9.

[@50sKid]

Normally anything lower than 5 isn't cause for concern. If you don't have any codes, then don't worry about it.

[@michaltimko]

@@50sKid I had same issue, invested lot of money...and my adaptations were always negative. I replaced almost whole fuel delivery system and after 2 years i found it was broken MAF cable. Replaced cable, adaptations went to +2%/+2%

[@ukaszteter6283]

did the pressure drop after replacing the fuel pressure regulator and turning the key to the second position like 11:52?

[@chuckworkman6322]

Have a ? I own a 2004 z4 2.5 I changed the ccv I disconnected the battery before I started and color coded the plugs so I wouldn't mix them up even tho they will only fit the right one but after I hooked the battery back up after completing the job and now it will crank but won't start any idea

[@typhoon1493]

great video! 1st i had an emissions code so i replaced the rear bumper valve at canister. code goes away. then, immediately i get a vacuum leak code. ends up being the oil return at dipstick tube. replace hose and code goes away. then, all of a sudden 420/430 pops up together immediately and now i can not get rid of those codes. car drives great and does not lack power. reach 30-35mpgs (highway) when being delicate on the throttle. so it's very hard for me to think both cats are bad. '05 330i zhp 6spd this video gives me something new to check out. thank you

[@likits1999]

Hi 50s kid, have you ever had a P1092 on an M54 engine? I have a 200i 330i with the P1092, I replaced MAF and O2 sensors, spark plugs, injectors, fuel pump and fuel pressure regulator, disa valve and smoke tested. The light still comes back. I'm about to go pay the dealer for a diagnostic but I thought I would ask your input before I go. Thanks in advance.

[@williamweatherall8333]

This is so helpful. I've been trying to figure out the cause of my rough idle.

[@pyrael668]

I'm wondering if you may be able to point me in the right direction. I'm getting a lean code (bank 1 only) and a insufficient flow on secondary air pump on an 02 e46. I have checked trims, all are less than 5% (-2 on long term and 4 to 6 on short term). Smoke test revealed nothing. Is there another possible cause? Air pump works, relay works, I replaced the vacuum lines to the air pump valve on manifold, tested the switch at the intake, replaced fuel pressure vacuum line and filter, replaced MAF. new upper and lower intake Oh and also replaced fuel pump which is running 40+ PSI. Thanks in advance for your reply. Love your videos as well, they have helped me eliminate all but these two pesky codes.

[@jbaroli]

check PCV valve and hoses.

[@pyrael668]

@@jbaroli Thanks!

[@bobcampbell4263]

50sKid Hi, excellent public service you perform. I have an e46 that gave a 28B8 code after I changed my oil!! I installednew cps and tested solenoids. Is this something you could help me with. bob

[@50sKid]

+bob campbell Actually, no. It sounds like the computer thinks there is a mechanical problem with your cam sensor, which possibly means that it's out of sync with the crank sensor. This is more of an advanced diagnosis subject and I can't help you with it over the internet. I'd advise you to find a technician who can diagnose it by putting your cam and crank sensors on a scope and determining what is wrong.

[@bobcampbell4263]

+50sKid Thank you for responding... is this something I could pay you to speak with me over the phone or via Skype for say 10 minutes...bob

[@toyotoe3732]

Did you have to put back the 20A fuel pump fuse before turning the ignition on to read the fuel pressure?

[@50sKid]

Yes without that fuse, the fuel pump won't run and thus won't make pressure.

[@NOKRBTZU]

I've got question I have problem with lean codes but no vacuum leak I did smoke test and pressure test. So the STFT at idle is near 0 like -1, 0, +1, 0 but if I accelerate it went to +22 this all was pefromed when the lean codes was deleted and LTFT was on 0. Thank you for your help.

[@ukaszteter6283]

Have you repaired the car?

[@NOKRBTZU]

@@ukaszteter6283yeah it was incorrectly manufactured air filter even it was new, tried another air filter then it was ok put back the previous and problem was back I think there was maybe some kind of turbulence affecting the airflow and MAF sensor…my theory… since that the car run well with fuel trims almost on zero…but I already sold the car and went to facelifted f30

[@ukaszteter6283]

Thanks for your reply, I'll check it out. I'm 0% at idle and 6% at higher speed@@NOKRBTZU

[@NOKRBTZU]

I had false air long time ago and I think this would be your issue too, the best thing how to find air leak is unmount airbox and put rubber glove on the intake especially on throttle valve make a hole in the glove put there some hose from aquarium for example duct taped it and use vape cigarette and just blow it inside the vapors and you will see if the glove will inflate or not and if not you will see the vapor or smoke coming from place where is air leak...do it with turned engine for sure!.... sorry for my bad english Im from Slovakia@@ukaszteter6283

[@iamurnamann8662]

I know this video is old, but I’m trying to find the normal fuel trims for a 2011 e90. Can’t find it anywhere. I want to know if my fuel trims are normal. Is there a normal percentage when the car is in hood health? Should the Trims be at 0 during idle? Are the trims in the negative during idle? I can’t find the info.

[@jsastre2031]

I can not read the STFT2 on e46 m54 325ci, it is always at 0, as my LTFT2. STFT1 is showing values. O2 sensors are ok, no fault codes and the engine runs ok. The last time I tested showed all values moving up and down (as normal) but right now all bank 2 is always at 0. Using torque apk and Elm327. Any suggestions? Thanks!

[@terrenceg3257]

Could you do a video on how to set up the hardware and software. How much should i pay for the Program? What features should I look for when purchasing the ELM adapter? Thanks!

[@andreiaugustin3809]

Most helpful videos on KZbin! I'm going to test as per your video as I have the same issues on my 2002 330Ci I recently bought, however there's one thing I was wondering about: previous owner had a CCV delete and I can see the dipstick and intake ports for the CCV are closed while the breather is venting to the atmosphere, in such scenario I don't think you'd have a significant vacuum leak since the intake ports are closed, correct?

[@robeaton2191]

Thanks for a great video, im trying to solve a P0171 / P0174 lean issue, i observed the short term fuel trims when warm at idle and at increased revs. At idle and increased revs im getting 25% on both banks, if i blip the trottle it stays at 25 then drops to 0 then back up again. Im pretty sure as the trims stay they same at increased engine speed this doesnt indicate vacuum leak, is this likely to be a bad MAF, my local mechanic did notice the previous owner had installed an aftermarket MAF. Thankyou

[@MrHaaaj]

Did you find the problen?

[@robeaton2191]

@@MrHaaaj My problems seems to stem from a faulty MAF, replaced and she's all good again.

[@1pizzadox632]

Thank you very much I really like your channel and from this video i realized i had to delete the adaptations because my short term fuel trim are +1 but my long term fuel trim are -4 and maybe then I'll figure out what the true values are.

[@jeffreychandler1477]

Hello, I have ax2006 bmw x5 3.0 m54 engine and I have the dreaded p0171and p0174 codes. I have tested my fuel pressure and I get 50 psi when the car is running, 46 psi with the car off and 46 psi with the key on in position 2 with the car not running. I have smoked the car and can find no leaks and have cleaned the mass air flow sensor and unplug the sensor with the car running a get a change in engine noise until I plug it back in. My codes are lean 10.9 in bank 1 and 9.4 in bank 2. What should I be looking at next.

[@YanGon-jt4yu]

My Fuel Trim stays at 27.3 even with disconnected MAF sensor, it only drops when I hit the throttle. Do you I still have vacuum leak?

[@patrickbryant_]

Your videos are a wonderful resource! I have a 2001 e46 330i with both banks running lean, long term trims around 10-11%. Short term fuel trims increase up to 10% under engine load suggesting to me that it is not a vacuum leak. I cleaned the MAF and no improvement. Fuel pressure at the rail is right at 50psi both at idle and when running. You say it should read 36-46 when running. Could clogged injectors cause the fuel pressure to be pegged high at 50?

[@patrickbryant_]

After some more research and thought, my new suspect is the pressure regulator vacuum line. My understanding is that we want the pressure difference between the fuel rail and the intake manifold to be constant. Since I see constant fuel rail pressure even when rev-ing the engine, it seems the pressure regulator is not adjusting to the changing intake vacuum

[@patrickbryant_]

This would be an interesting problem because the fuel pressure would be higher than desired at idle which you would expect to generate negative fuel trim but the vacuum leak could cause it to run lean, this would explain my +10% long term fuel trim. Then at high RPM the throttle is open so the intake pressure rises to nearly atmospheric pressure but the regulator does not compensate with increased fuel pressure so the O2 sensors would see a lean condition and the short term fuel trim would go up.

[@patrickbryant_]

Ugh ok this theory seems wrong. Turns out the air pressure reference line in these cars isn't the intake manifold vacuum but rather is a Venturi line to the intake boot. this seems to have almost no effect on the fuel pressure.

[@patrickbryant_]

Solved! Picked up a new Duralast MAF for $116 and long term fuel trims returned to ~0% after a few miles on the highway.

[@joehinkle3603]

hello Jason recently replaced ccv all vaccuum hoses on my 04 330ci rebuilt disa with g.a.s. kit. the service engine soon light is still on disconnected batt still is on do i need to erase the codes in order to reset the light. codes show bank1 bank2 lean also shows replace pvc valve which i have already done.your videos and your help is greatly appreciated.

[@fr0ilan]

this is awesome! I've been chasing fuel trim problems on my e46 for over a year now. Thanks!

[@50sKid]

What do your numbers look like?

[@fr0ilan]

I still have to check the values. I've done a smoke test, found some leaks and repaired them, yet the codes still come back for both O2 banks. I use a peake tool and E3, E4 keeps coming back. I'll come back and update you. Thanks.

[@ashleywilliams9050]

Trying to get to the bottom of some issues my daughters BMW is having. She has a 204 325i SULEV that has had the fuel tank swapped prior to us. Fuel trims (at idle) are as follows: STFT B1 16.6 LTFT B1 18.8 STFT B2 16.4 LTFT B2 18.8 When holding RPM at 2000 STFTs drop to normal range. This is an indication of a vacuum leak? LTFT don’t change, is that an indication of dirty, or failing, injectors?

[@chadriddle3517]

Excellent fuel trim Tutorial

[@allenbryant5953]

Very informative, I now completly understand how the fuel trims work now. Dude seriously, are you a teacher or professor in your day job?

[@ducewill]

Sir you are great , excellent videos very easy to understand I watch you from Mexico and just change my Thermostat without the locking tool ... You are saving me a lot of pesos !!!

[@50sKid]

+Guillermo Renato Salazar López Gracias!

[@aor3200]

Thanks, really great M54 diagnosting. Great video and keep up good work.

[@macknumber9]

Why is long term at 0%? Did you reset the PCM? I would imagine if you had a fuel delivery issue your long term trims would definitely be more than 0%

[@chrispirrone7798]

I have a e 46 2001 330i and the same codes keep coming up no matter what I try post and pre cat fuel trim codes p1190 p1191 p1192 and p1193 any in put would be helpful

[@YanGon-jt4yu]

Thanks a lot! Keep posting about E46.

[@iGMAS]

Hope you will see this. I had fuel trim on bank2 of my m73 up to 20%, did your tests and found out its a vacuum leak(I sort can hear it). But I fixed the fuel trim issue when I removed the Air Injection valve it went to almost perfect 0%. Why is the air injection valve causing a fuel trim of 20%?

[@adamb50]

This video was on point, very helpful enjoyed watching Thanks man!!

[@HtMnBrusso]

I’m a little confused at the MAF part. What constitutes a good/working MAF? Does it have to read a certain amount of airflow at idle. I unplugged mine, engine didn’t stumble and the ST fuel trims stayed positive and didn’t drop suddenly negative. I have a similar engine, not sure if it works same as your example 2006 X3 with the M54B52 motor.

[@ProducerGio]

You're God sent. Thank you for all your hard work.

[@normansilva8403]

Wats up Mr 50 You said to watch out for cheap mass air flows on eBay. Can you tell me why? They go from 20 dollars to 300.

[@50sKid]

They don't work. Instead of using a more expensive platinum wire they use a cheap resistor.

[@normansilva8403]

Yo 50's dude!!! Any chance you might have a link to that software you used? I tried looking it up and got all confused.

[@ramazkutateladze538]

Hi, what if the STFT indicator on an obd scanning program reads N/A on both banks.. ? I get the voltage indications on upper banks but STFT says N/A :( it throws P0170 P0174 and until I get money to repair, I do reset the ECU..

[@genef-body8441]

My lt fuel trim is negative 5.5 short term bounces from 14-22 positive both banks unplug maf drops down to -1/4 new disa clean maf and car is in limb mode

[@Bavarian_M]

Hey 50skid I have lean code on back 1&2 and rich on bank 2 I read the fuel trim and short is at 6 and 7 and long trim is at 11 on both when press on the Gas short trim goes to the negative. Any ideas where I can start

[@CMDRRustyDog]

Superb video. Well explained and answered all the questions I had.

[@jonapolloapollo5770]

Can you help any ideas on a p1580 m52tub20 something to do with the throttle body maybe you have com across this type of problem hoping I don't need a new TB Thank you KID

[@petediamond7263]

What if you only had a P0174 code how does a vacuum leak apply to only one bank how does fuel pressure apply? Thanks chasing a problem can't find it!

[@TamilTexas]

I have the same problem. How did you fix your problem? Thanks in advance.

[@petediamond7263]

@@TamilTexas I did the 02 sensor broke off internally who would every think.

[@bjenks2]

@50skid I have a p0150 on my 1998 740il. The car feels like it's misfiring but the coils and plugs are new and good. I looked at the fuel trim and when it shakes the fuel trim drops. But when it rises it's fine but it rises above 20. Is this because the precat o2 sensor is bad on bank 2? The bank 1 sensor and fuel trim look fine; they go up and down constantly staying within +/- 10.

[@50sKid]

If your fuel trim rises to 20, that is a lean condition. If it goes down when you raise the RPMs to 3000, then the cause is a vacuum leak.

[@bjenks2]

Thanks, I'll see if it goes down when I raise the rpm to 3000. If not could it just be the sensor? Yesterday I had pending p0150 p1509 & p1550, still could be vacuum leak?

[@50sKid]

Ok sorry I didn't look up that P0150 code the first time I responded to you (sometimes I have a lot of msgs to go through). P0150 is O2 Sensor Circuit Malfunction Bank 2 Sensor 1, which does point to either a bad O2 sensor OR a problem with the wiring. Check the wiring integrity on that sensor before you replace it (meaning check for continuity between the white and black wires in the harness). The other 2 codes are idle control codes which could be caused by the bad O2 sensor--so start with that.

[@bjenks2]

Ok thanks sir

[@josemartinezoc1534]

50sKid. great video ! and very clear . 👍 i have a question. and i just want to clarify so does fuel trim banks staying at 0 a good thing ? because you mentioned anything above 10% is adding too much fuel and anything (-) is removing from too much fuel right ?

[@alexangulbudaghyan1781]

Hey @50sKid thanks for detailed instructions, can fuel pressure regulator also cause missfiring codes with p0174 and p0171? I have p0174 p0171 p0305 and random missfires code

[@50sKid]

I doubt it. You would have to have a severely restricted fuel filter which usually doesn't happen. P0171 and P0174 are almost always caused by vacuum leaks.

[@alexangulbudaghyan1781]

50sKid thanks for reply, i noticed that the first code that is thrown is p0174 and only after driving a while i get p0171, does it have to do something with SAP or it will be triggered only on cold starts?

[@50sKid]

+Alexan Gulbudaghyan if it was sap you would also have sap codes. You have a vacuum leak somewhere. Watch my common vacuum leaks video

[@robert860212]

50sKid Hello can some one help me i have this code P0170 fuel trim bank 1 My engine goes uneven and turns off when it's in a minute and can not run it at all because it loses all the Power i changed air flow meter but is stil The same i have dont change fuelfilter and power train regulator on the last i scaned it on garage with data tool scanner and I get catalytic fault code Could it be wrong that it goes uneven i Will be very grateful for respond back Thanks

[@smvk666]

Great video, very instructive but your engine still sound funny at 14:16 some kind of ticking and wobbling, maybe a pulley is bad ...

[@normansilva8403]

I’m sure you heard this before but THANK MAN!!! If your ever out east come to the Hamptons We’ll smoke a bowl!!!!

[@georgesantana2293]

Hi 50s Kid, I noticed on this video after you installed the new fuel filter/ regulator the pressure at idle was 46PSI. Next time you measure fuel pressure would you confirm whether the 46PSI changes at all if the small hose at F tube is disconnected? I would expect it to rise to about 50PSI while hose is disconnected but would like to verify. Thank you.

[@50sKid]

+George Santana I've already told you 4 other times that it is now 50psi, all the time, which is normal. When you disconnect the vacuum line, the pressure does not change. How much clearer do I need to be on this? Your fuel pressure is normal.

[@nikhilrw]

Brilliant video and information! Glad I came across this.

[@Steev74]

Love the internet. Thanks for sharing and explaining so well. I'm gonna have a look at my fuel trim.

[@frightman91ify]

Hi , i have 330 ci and i have positive 10 percent on idle and it will decrease to 0 only once i hit the accelerator or if i let the car idling for long time , no vacuum leak spotted an as i test the vacuum system and no codes , what it could be the issue ??

[@strivezoul]

Positive fuel trim means bad fuel consumption, right? Right now my car doesn't throw fault code, but my fuel consumption is very bad, usually at 5.5km/l or 13mpg. This is with city driving only and i drive mildly. Also when i opened the oil cap, i out my hand over it and i didn't feel reasonable suction from it. I only have pa soft scanner, not sure if i can check fuel trim with it.

[@50sKid]

Yes positive trim = bad fuel consumption. You're not supposed to feel suction on a stock system. No you can't check it with pa soft you need an OBD2 scan tool. Search my channel for my review on the foxwell one. Cheapest one I have found that can read live data.

[@strivezoul]

50sKid ah alright.. i thought there should be suction because when i compared it to my honda or my wife's nissan there is quite strong suction from the engine oil hole. I do have the exact obd adapter you mention the first time in this video, my is bluetooth version and it once worked but no longer, i don't know why. I was never able to read freeze frame using obd fusion android app. I also have 2 others, tahg won't work at all with this bmw but the other one works with my honda and the other last one never worked with my cars. I have cable that should work with inpa/ediabas, but have never got around to install it till now. Does it have live fuel trim data? Thank you for the video, i watch most of your e46 repair videos, they are very helpful. :):)

[@50sKid]

The data that you will read from the pa soft and inpa cables is BMW's "additive" and "multiplicative" fuel adaptation values which are different from obd2 fuel trim percentages. Not helpful

[@abcges]

Hello, So what are your thoughts on aging sensors? I have a kind of interesting problem but a little theory first(skip to last paragraph if you have no time). With M52 they used Titania sensors that lasted a long time but looking at my M54 voltages i'm reading zirc values (up to 0.9 V etc), so sensors are probably more prone to aging problems. Anyway according to my logic a vacuum leak would cause high trim because of the higher amount of unmetered air resulting in a lower amount of fuel being injected according to fuel maps and because lambda sensor catches the excess air due to lower amount of fuel injected, it will add more fuel and thats why we see higher numbes on fuel trim, same thing with dirty MAF (lower air). My E60 M54 has a little rich idle i think, because although i can not smell rich exhaust, during colder periods it has a little too much condensation at idle coming from the exhaust. I presume my cats work fine and thats why i cant smell rich exhaust and they transform the unburnt fuel into H2O. It's not just the normal higher condensation that occurs during winter etc of that i am sure, because it still happens after longer drives and is always there, even when all the other cars around do not produce "condensation vapors". My fuel trims are fine and i have no codes, lambda voltages are fluctuating like their supposed to, so i'm thinking the ageing oxygen sensors are the culprit since the effects would not even be registered by fuel trims and the sensors are "bad" due to voltage not reaching that high anymore?

[@abcges]

All the other problems that would cause rich mixture would probably be picked up by oxygen senors and in turn by fuel trims i would guess.

[@codyfoster3205]

Would this cause limp mode? I have p0174 and p0171 but go into limp mode at freeway speeds. Its a getrag 5 speed so its not a transmission limp mode.

[@Heethoofd40]

Did you solve this problem?

[@tonyhuggins6407]

i have a 2003 x5 what is the color code for 02 sensors that determines rear or front

[@boopunn]

Hi. I have a bmw X5 with M54. Brand new motor but it runs rough when cold and fuel trims are 25+ on both banks. I have checked the fuel pressure and it is at 50 steady. I am working on building a smoke machine but everything is new. I replaced the pcv system tried 2 different IDC's and Disa valves. New MAF that is platinum based not the cheap version. I know i have a bad O2 on B2S2 it stays around .400MV B1S1 is about .05 MV B1S2 is about .05 and B2S2 is .10MV . The system does tell me B2S2 is out of range. I guess my question is, can the one O2 sensor throw the STFT's off by that far? Thanks I used your videos to help me build the motor.

[@boopunn]

Oh and the fuel trims do not go down when I bring up the RPM,s to 2500.

[@50sKid]

Yeah if your precat O2s are not oscillating between 0.1 and 0.9 something is wrong. Replace them.

[@boopunn]

Thanks. I ordered all 4 new so i know they are all good. If i unplug the MAF it will let it idle ok but the bank 2 STFT is still high from the bad O2. The odd thing I am seeing now is that if I plug the MAF back in (old or new) then all 4 O2,s go nuts and do not show properly. With it unplugged the front bank O2's are acting normal. Would the B2S2 being bad make the MAF mess with all of them? I guess I will find out when I install the new O2's.

[@tamhamill5274]

Andy williams Did you get this problem fixed bud

[@reubenquiroz6083]

@@boopunn I'm a year late. Did 4 new oxygen sensors fix your positive fuel trims of +25 on both banks?

[@jorgeavila3131]

You solved the problem í have a bmw325i 2003 with the same problem fuel trim bank 1 and 2 that must change?

[@blainegabbertgabonemhofgoa6602]

12:20 do you put the fuse back in or start it up without again

[@matteomoretti1978]

Forgive me for my bad english. I have a problem similar to the one in the video. My short fuel trims are about 25% at idle. I've checked for vacuum leaks with a smoke machine but I've found nothing. The MIL light is on with P0150, P0170, P0173, P1250 and P1520. I've bought the car 2 months ago and since then I don't know where to look. The O2 sensors are ok (checked voltage), i have changed the oil and fuel filter 4 days ago but nothing changed. The MAF is working properly (I've also cleaned it but no luck). The fuel trims when I start the car are about at 3%, then slowly go up at ~25%. When accelerating they drop at 11% but they won't go down over that. I don't know what to do 😪 Thank you for any response

[@kingsconsultingcarrepair2884]

My e39 is constantly running rich.... what are possible causes

[@carlosagustin8465]

I'm having the p0171 code Bank 1 running lean on a 2005 330i I've taken it to the mechanic because it had p0171 and p0174 and they were able to get rid of p0174 but the p0171 code keeps coming back could it be the fuel regulator? Because they've connected a smoke machine to the car twice and haven't been able to find any more vacuum leaks from when they found the first two and got rid of the p0174

[@50sKid]

You watched this video. What type of lean condition do you have?

[@carlosagustin8465]

50sKid A positive fuel trim

[@50sKid]

Yes a positive fuel trim means lean condition, but what type of lean condition is it? Is it a vacuum leak or is it a fuel delivery problem?

[@carlosagustin8465]

50sKid right now I'm thinking it's a duel delivery problem because we've connected a smoke machine to try and find any vacuum leaks and we've found 2 but those are fixed and the code is still appearing

[@gavinbaumanis6078]

did you clear the code, before rescanning? Or are you just getting the old code over and over?

[@mcycleserv]

great vid again trying to learn about E46 fuel trim ..never had this when I was working on cars back in the 70's I have torque pro app on the car DVD and there are a few questions I hope that you can help me with these figures I have LTFT1 =11.7% LTFT2=11.7% STFT1= -0.8% STFT2= +8% O2 1x1 .06v O2 1x2 .07v @-2.3v stft O2 2x1 .04v O2 2x2 .04v most of these figures fluctuate but LTFT stays the same I am concerned with economy being 9.4km/lt to city 6.5km/lt now my DISA I think is not working because after I removed it and checked out the unit I sprayed WDF to check diaphragm which started working and would hold flap .. when I refitted unit there was a vacuum noise from DISA at idle ...unplug connector to DISA and noise stopped indicating diaphragm has a leak cause flap returned to center ... funny thing is the motor idles perfectly and car has heaps of go but!!! have ordered a DISA complete kit from Russia so have you any thoughts on these figures I am going to get that program Scanmaster because of how you described how it worked and is easy to load to pc am a bit concerned on fuel economy

[@50sKid]

Yeah your long term fuel trims clearly indicate a lean condition. Over time your car has "learned" that you always need 11.7% additional fuel beyond normal. The short terms fluctuate because they are the immediate "right now" fuel trim corrections. The key thing to understand is that you ALWAYS have to add short to long to get TOTAL fuel trim. In the video I say that when you rev your engine to 3000 rpms, your fuel trims should go down if you have a vacuum leak. In your case, since you have 11.7% long term and let's say about 0% short, when you rev your engine, your short term would go negative--let's say -9% for example. When you add 11.7 to -9, you get 2.7% total fuel trim. Is that making sense? Is this what happens or does it stay the same or go higher?

[@mcycleserv]

it stays the same ..was 11.7% before I did work I have just replaced leaking valve cover and filter body seals and the valve cover breather to CCV that was cracked and someone taped it up with electrical tape done Vanos seals and spark plugs oil and filter and fuel filter removed neg batt lead and pos connected together for 10 minutes there are no codes so I better get the Scanmaster asap and try and trace maybe airleak maybe the Disa has a small leak that does not whistle but is not enough to bring up a code I have PAscam 1.4v on pc but looks like scanmaster might be better showing fault codes

[@50sKid]

The thing about BMWs is the long term is slow to respond to changes/improvments. While the car is running, unplug the MAF sensor for a moment, then plug it back in. That will reset the long term fuel trim to 0 so that you now can see everything in the short term fuel trim. Then repeat the test where you run the car at 3000rpm. Be sure to hold it there for a good couple seconds so you can see it respond. Tell me what results you get then for fuel trims.

[@mcycleserv]

have to do that when wifey brings car back later thanks for ya help...oh one thing ..do you ever sleep haha ???

[@mcycleserv]

ok have readings started car unplugged MAF replugged and held revs to 3K+ readings STFT 1 27.3% and then dropped to 0.0% after a minute LTFT 1 0.0% STFT 2 27.3% then dropped to 0.0% LTFT 2 0.0% O2 1x1 0.1v 1x2 0.4v 2x1 0.0v 2x2 0.4v