STFT reads opposite of LTFT (after repair fuel trim data)

In this video I locate and repair a vacuum leak. Then I will show you how to use fuel trim numbers to determine whether or not the lean exhaust (P0171 and P0174) fault codes have been fixed. There are times when you have multiple problems, multiple leaks and the question is, are you confident enough in your repair that you know that check engine light is not coming back on? Without running any type of drive cycle, are you confident enough to give the car back to the customer?
Understanding ST and LT Fuel Trim • Understanding Short Te...
For more information on this topic, I have written a “field manual” called Engine Performance Diagnostics which is available at www.scannerdanner.com as an eBook or paper book.
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On ScannerDanner Premium I will bring you right into my classroom at Rosedale Technical College. You will find page for page lectures taken right from my book as well as exclusive classroom type case studies. What is so special about these classroom case studies? I pull live problem vehicles directly into my classroom and we troubleshoot them in real time, using and applying the theory and testing procedures we learn during the classroom lectures. There is no better on-line training of how to troubleshoot automotive electrical and electronics systems anywhere!
Disclaimer:
Due to factors beyond the control of ScannerDanner LLC, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. ScannerDanner LLC assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. ScannerDanner LLC recommends safe practices when working with power tools, automotive lifts, lifting tools, jack stands, electrical equipment, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video. Due to factors beyond the control of ScannerDanner LLC, no information contained in this video shall create any express or implied warranty or guarantee of any particular result. Any injury, damage or loss that may result from improper use of these tools, equipment, or the information contained in this video is the sole responsibility of the user and not ScannerDanner LLC.

[@CornFed86]

I wish more people took the time to figure the problem out. I've thrown Alot of money at p171 and 174 on 4.8 vortec. New pcv valve, fuel filter, fuel pump, plugs and wires. Same codes 171 174. Thanks man you rock at what you do!

[@jeffjohnson3195]

Great video, and that smoke machine really does a great job. Makes a world of difference to understand the fuel trims....

[@MortoFett]

Very coherently explained as all ways, I'm sighing up for the premium channel.

[@rexreid6915]

Thanks ScannerDanner you are a huge blessing.

[@edwardthayer9386]

Engine temp is 185 on highway speeds. Thank you very much for your time and help. I'm really stuck on this and have to get it inspected. Anything else and in on it!

[@ScannerDanner]

185 is a little on the cool side. Is it easy to change the thermostat on your car? If it is, do it

[@nemanjadzombic6101]

Bunch of useful information as always. That smoke machine looks professional.

[@everardocamacho5063]

great video Mr danner, I'm happy to watch your videos they are very instructional to me, specially this one and others about fuel trims

[@yaseenhashim8538]

thanks Mr scannerDanner awesome top diagnosted

[@geojor]

enjoy your videos, you put a lot into them...

[@gen-X-trader]

wild. i had a p0171 / 174 lean combo. found the vac leak. also had a sluggish maf that had weird dips and pauses in the lb/min rate. fixed leak. replaced maf and the short trim at light throttle is -20 while the long trim is around +20. it runs great now but i was really curious what the heck is up with those numbers. thanks for explaining that and what i see is just verifying the fix

[@ScannerDanner]

Awesome!

[@Thunderroad8517]

Another awesome teaching there Paul! Thanks Man!

[@ScannerDanner]

Thanks Michael

[@acrittendoncrittendon4143]

I like that my wife suv is a 06 same code also and I bought a smoke machine to do the same test wow so cool. Same model and make and engine

[@Eddythe_Eagle]

I have a 2010 elantra with a rough idle. really rough the first 10-15 sec on a cols start. Continues to run less rough when engine hot at idle. Worse under load. STFT is )(-1.6 to -0.8) and LTFT is (-4.7 to -3.9) Should these trim number be reverse. Is this a lean or rich condition? Seems like it is taking away fuel? Any answers ? Rich or lean condition. Poor gas mileage, worse power on acceleration.

[@alexbrophy6885]

Loving the modis ultra :)

[@fortnitedaily1042]

Hello, i had negative fuel trims in my car like -18%, los of power and bad idle, i changed the maf the car run very smooth now, and have much more power but Ltft has gone -25%. Any idea why the fuel trims went more nefative but the cur runs better? Could be the ne maf faulty as well??

[@Pablo_Automotive]

Fantastic work¡ This videos is excellent.

[@wajeehulhassan2182]

i chked my car by scaner....maf reading was good short fuel trims was well within range going +3 to -3 But long fuel trim varied but was in the positve range only.... I changed my fuel pump yesterday also i have my injectors serviced.....is it ok or what should i do...

[@jgeorges3061]

thanks dinner, good info as always.

[@hrfb9696]

I get high ltft in one bank at idle in my 2005 prerunner . Can’t find a vac. Leake. Any suggestions? Thanks

[@ozzstars_cars]

if that smoke machine wasn't so expensive I'd buy one. Until then I have to light up a cigar and blow my own smoke.......you know where. lol Take care man

[@markr78]

I have a 98 bonneville k engine and using fuel trim I fixed vacuum leaks and replaced all intake gasket and egr tube leak .I have a p0171 code and 300 code intermedi not all the time I did a tune up but still same problem the only thing I noticed after I changed upstream o2 my downstream 02 moves very litle in idle but more during 2500 rpm what should I do I have 2 short term and 16 long term now it won't change

[@nicorallysport]

Please, can you help me to interpret my short term and long term trim, my Focus RS mk2 of 2010 18000kms (~ 11200miles) with a preparation stage 3 (injectors big debit 650cc, remap, intercooler big volume , complete exhaust line decat, dumpvalve, plenum mountune etc ....). So cold engine my STFT and in the negative (normal view cold engine enrichment I think), once hot engine the STFT oscillates between -4% and + 4%, but the LTFT still remains at 0% is this normal ?. Do you think that with its figures there is a vacuum leak where everything is normal? thank you beforehand. Best regards. Nico (ps = sorry for not understanding english :-()

[@whitetiger8652]

Nice smoke machine Paul.

[@mariuszanfir2298]

Hmm, I thought -/+ 4% LTFT is what would be considered normal. Does it differ from manufacturer to manufacturer?

[@haycall]

You Rock bro!!!!

[@chrisisho2557]

What mean if I have Zero short term and 27% long term, i have P0086& P0106, No vacuum leak at all, LTFT keep checking all times between 27% to 18% but never go less 18% whatever RPM, you think there vacuum lean or bad fuel delivery ?

[@ScannerDanner]

Define the other codes.

[@chrisisho2557]

@@ScannerDanner both codes related to the MAP sensors,

[@trainer2018]

See you have a Modis Ultra, what do you think of it so far Paul? Thinking of getting the Ultra or just the new Edge.

[@besofacacia6103]

thanks for video man. i did so many things on my x3. but if u want to do something good u must do it yourself. i was just forced to bye odb2 blootooth reader. at last i found adjuster unit leak today as i was in hurry (its very hard to take it off from x3) i could take it out by half , cleaned as put some sealant around. i need to make some more as i found but i got stft -10 and ltft +14+16 and if u say its normal well thanks a lot. :)

[@ScannerDanner]

+beso facacia nice job understanding that and I would call that a fix

[@Poocang_golfr]

do you know why my car shows -100% on short term fuel trim B1S2?

[@teresahoffman1300]

Need to know what are good fuel trim numbers. How do you know? Not all understand domestic tools What are the moral fuel trims 1and 2?

[@ScannerDanner]

kzbin.info/www/bejne/pYO7Y4lslMZmmsU This video is for you my friend.

[@SteveRobReviews]

Nice- I noticed the increase in the MAF after the fix. Besides increasing the rpm to help in indicating a vacuum leak or not is there another pid you have noticed is another good guide to use for a suspected vacuum leak ?

[@DENicholsAutoBravado]

+Steve Rob For the few cars I've applied similar information on, I've found the MAF to not be a reliable tool for vacuum leaks. It points at the fix, but not so much at the initial problem to be fixed. General statement over, I've noticed a subtle change in MAF g/s get reduced, and more importantly, a better idle and a lower idle that's closer to normal be more of an indicator.

[@SteveRobReviews]

Besides the MAF , i was just wondering if another pid could be used as well , I don't know so I thought I would just ask and find out 👍

[@DENicholsAutoBravado]

Steve Rob With the last vacuum leak my IAC valve opened even more, opposite of what it needed? Sure, but it was responding perhaps to the overreaction to the O2's demand for more fuel as a result of the vacuum leak. Another pid...he commented on the RPM for good reason...it's safe to assume the TPS worked fine with the vacuum seeming better at more demand of course. I like to watch the upstream O2 sensor to verify the STFT correction. That's all I can try to add to your great question. Scanner Danner has blown my mind some times, hopefully he'll respond. :)

[@SteveRobReviews]

The only pid I could think of was the MAP at idle but like all pids you must know what a normal reading is. If I'm not mistaken the high rpm and LTFT reduction has not always been foolproof for Paul. Interesting stuff Ah....

[@DENicholsAutoBravado]

Steve Rob Oh, that's really good. Gives you a chance to distrust the MAF.

[@bigj6867]

Nice one

[@briansturgill5905]

Getting perfect STFT and LTFt almost 0 on both. When I come up to a stop light STFT go to +25 then couple seconds go back to right around 0. Then CEL for both banks lean will trigger. This only happens when I’m running the AC coincidentally. So frustrating.

[@ScannerDanner]

Brake booster leak maybe?

[@bgregg55]

using the brake booster line can backfire if the leak is in the booster itself. i just got caught by this one. the brakes worked fine & there was no noise but there was a very large hole from corrosion in the bottom of the booster. also, a $35 fog machine can be used as a crude smoker for those who don't want to spend $1000 for one.

[@ScannerDanner]

Absolutely! I did one on a Pontiac G6 and that's what it was. I'll post the link

[@ScannerDanner]

m.kzbin.info/www/bejne/Z3bEYYagrcSNjqc

[@jbur9135]

Ran into this same exact problem several times on these engines....people take the box off and don't put the breather hose back on correctly.

[@stonecold0469]

hmm, nice vid... but got a question... for instance. 2007 Mazdaspeed 3 at idle. if i have relatively normal long term fueling 0 to 4 % and short term is stuck a -25.x % what does this means? thanks in advance

[@justinballard2168]

The car is running rich and the computer is taking away fuel.

[@charleslarrimore6521]

I have a 2000 Toyota Celica 1.8 take GTS it idles fine bogs down when I first touched the gas how's your new fuel pump new throttle position sensor no engine codes just trying to get pointed in the right direction

[@ScannerDanner]

Post this to my forum. It is free to join and we can definitely help you there. www.scannerdanner.com

[@midwestriders1]

So If you have a fuel trim of +25 and then spray around the intake and it drops down closer to zero that is where your vaccum leak is right?

[@besofacacia6103]

yas i fixed mine like that.

[@edwardthayer9386]

Ok just got done changing the thermostat with one bought from the Hyundai Dealership. I've drove 72 miles and I'm at the same exact temperature. 185. All my monitor have set except o2s. Isn't there any tests I can do. I'm really not trying to keep throwing parts at it. That's honestly why I can to you because I thought you were really big against that. Just like me. Anything can be properly fixed with proper procedures. I've even asked on your forums but nothing. Well 1 fella did suggest unhooking the battery, which I've done and did again just because he was nice enough to respond. Everything set except o2s. And now I'm driving with dead tags till I can fix it. What would you replace next? Oxygen sensor and air fuel have been replaced twice even though they tested good.

[@ScannerDanner]

of course I don't want you to throw parts at it, sorry for the suggestion about the thermostat, I have nothing else to offer you, sorry, I wish I did

[@ScannerDanner]

"What would I replace next?" nothing, I would need to see the car and I don't have that option. You may not be doing the drive cycle correctly for that monitor to run. All cars are different. This is another comment where you seem to be pissed at me for suggesting the thermostat. I asked you if it was easy to do and you never replied, you just did it. So that tells me that it was. Yes, we changed a part, but so what, it was a $10 part. And it is a known issue (engine too cold to run a monitor). Also, why were the O2 sensors replaced in the first place? If you are going to be respectful, we can move forward, but lose the accusatory tone or I'm done.

[@edwardthayer9386]

@@ScannerDanner let's try this again! First I'm not pissed off! I'm not one of them clowns! Frustrated (YES) but not pissed off. My name is Ed, I live here in Delaware. I use to work for Lexus of Wilmington for several years. I left because I could take what they were doing to customers. Example= charging customers 14 hundred for a timing belt job but only changing the wiper inserts and oil change. That was my work order, my writer said we didn't have time for that plus the car ran great according to him! Yes I got the hours for the job but that's not cool at all. I had it made there but I cared about fixing people's cars correctly. I now have a small shop here in Delaware and have a pretty good clientele list. Plus I do alot of cars for postal workers in my area. I'm not the best mechanic and don't have the best stuff but I won't bullshit a customer or take on something I'm just not comfortable. Now about you, I honestly appreciate all you do and support you the best I can( like now I'm not asking for a hand out, I will gladly send you money first for your time and help) I believe you're like me but just alot better technician. I'm trying to get better but it's on my own. It's just me and my dog. So I knew I could reach out to you and most likely get this straightened out with your help. (Even though I know I was throwing parts at it I didn't question you, I just did it. Even though I was 99.9% it wasn't going to help. I respect you that much) what I was bothered by was after I changed it (honestly no big deal! I wish it was 10 bucks though! lol) I was hoping you'd help me the best you could. But I felt like you were like that's it beat it. EVEN THOUGH I KNOW YOU DIDN'T MEAN IT THAT WAY! I was hoping you'd ask me something about the car or even to try something else. I know I can get this car fixed if you'd be kind enough to help. I'm sure you have a life and family and I job, and I fully respect that. And that comes first as it should. And I understand you have to work through me and you don't have the car. That's why I'm willing to take any of your suggestions. Alot of issues I ran into just your videos have saved me. But this time is something different. I've never seen anything like this and honestly don't know what to do. I've done the manufacturer's drive cycle to a T for this car along with God only knows how many others. The car runs absolutely great, it just turned over 100k, all the monitors set except for the o2s monitor. I'm sorry if you misunderstood me! And I hope I've made the situation more understandable now. It's hard to tell how someone is feeling or acting through just text. I honestly thought you'd be curious about something like this if you've never see it before. I really pride myself on my work and how people feel about me. I know you could probably easily fix this if it was there. But you have to work through me. And I understand that can be frustrating. If you look at my previous post, I've always been very thankful and appreciative! (NOT LIKE YO CAN YOU FIX THIS FOR ME) I'm not like that. I honestly respect and look up to you enough by reaching out to you. If you don't want to help or can't I fully understand that. I was just hoping you cared a little more. Maybe you do and I wasn't understanding correctly. But if you willing to help I'd greatly appreciate it. If you want money my email is [e-mail]. let me know how much and how to send it? I gladly will. If you want me to perform a test or whatever I'm on it. I really respect your input and fully realize that it's not as easy as having the car there. I don't know exactly what you want to know about the car so I won't just keep blabbing but I believe you asked how this started. The car came to me for service, oil, air & cabin filter, trans fluid, tire rotation and check engine light. Plus I said I'd get it inspected for her. It's an older lady. Super nice. Code I had was OF COURSE P0420 but I was highly suspicious. Monitors were all complete at the time, just the CEL. One code. I did my maintenance, ran my scanner and saw rear o2 was pegged 25% and not responding at all. Front air/fuel sensor was real sluggish. So I recommended the sensors. Plus I realized the previous person that was working on it destroyed the o2 plus and the harness plug and had it all taped up. I removed the plug housing, test all my wires, they were good and in great shape. Wires to ecm, fuse box are all good. I put the new connector housing on, tested again, all good. I had a permanent p0420 but after the drive cycle it cleared itself, all monitors set except o2s. I researched and researched, tried slot of things, drove alot. Then I reached out to you. All my monitors will set except o2s. Last night I even got all the monitors to complete except o2s in 1 drive cycle. I TRULY APPRECIATE YOUR TIME AND HELP! If you'll continue please let me know what I could do now or what you may think. Thanks again. I hope all is going the best it can for you during what's going on. Take care.

[@z31freakify]

97 f150 4.2 St ftrm1 -2.3-+1.6 @idle St ftrm2. -2.3- +.8 @ idle Lt ftrm1 4.7 Lt ftrm 19.5 What could cause the bank 2 long fuel trim to be so high? Goes to 0 as soon as I press the gas. Vac leak? Exhaust smells rich as well.

[@mikeb5981]

You ever figure it out?

[@z31freakify]

@@mikeb5981 Blown head gasket. Had low compression on that bank, replaced both head gaskets and had the heads rebuilt. But still check for vacuum leaks, more common than a head gasket.

[@FieTraxxBeatz]

I've got a very rough idle. Sometimes feels like it wants to shut off. Checked fuel trim last night and LTFT bank 1 went as high 16.4 and bank 2 went as high 7.8. When holding at higher RPM's bank 1 went down a little bit, but bank 2 went up a little bit. What's that all about??

[@ScannerDanner]

+FieTraxxBeatz check it for a vacuum leak first

[@FieTraxxBeatz]

+ScannerDanner I don't have a smoke machine so I tried the cigar test. Also a vacuum gauge tester. Even tried spraying water around the intake and the vac hoses. Found nothing.

[@asonafro]

Hi Danner, i repaired the STFT -13 and LTFT -11, both are negative value by cleaning the MAF sensor. However after repair I rescan with OBD and got STFT between 0 to 3 and I can see that LTFT is learning and sometime get around 3%. However after test drive my STFT play around 0 to 11 and LTFT stuck at -11. I know in total total trim will be 0 because STFT is +11. But, Why the LTFT stuck -11? Is it because that cell not learning anymore? Looks like STFT want to trim but LTFT was stubborn to follow STFT. I still not disconnet battery yet and will do it tonight and rescan tomorrow morning and see if LTFT had improvement. Is it ok if STFT +11 and LTFT -11 after disconnect the battery and stay like that for long period of time. Appreciate your thoughts. Your follower from Malaysia.

[@ScannerDanner]

It sounds like you fixed it but the long term didn't quite learn yet. You are absolutely fine to keep driving it, or do the battery disconnect (cap discharge) to reset the memory.

[@asonafro]

@@ScannerDanner thanks for your reply. Do I need to worried if the scanner said my 02 test not complete. Other test are complete. From where I live we don't have to do emissions test like some states in the US where they are compulsory for emissions test. If my 02 test not complete does it will effect the car performance? From my internet research I found out that this 02 test will complete itself after do the drive cycle run. Still not doing it. But if it's not affect my engine performance i will let it reset itself after i take long trip in the future. And will not worry about it for now.

[@scannertz6505]

Hi. Another amazing video! What about the vehicle that has MAP sensor. It could be a vacuum leak? I got Hyundai Sonata has only MAP sensor (2010 2.0 LPG engine) LTFT is +16 and higher STFT is oscillating +1,6/-1.6 at idle. STFT is +16 and higher LTFT is fixed +1.6 At 2500rpm. If increasing rpms, STFT goes positive high No check engine light comes on. Is it a fuel delivery problem?

[@jygogaming3550]

Could be dirty maf sensor

[@ngstudios3796]

Enjoyed watching the video Paul , thanks. Wouldn't another option be to use the scanner to erase the previous fuel trim values and then check it fresh after the repairs are done? Have you got any videos that explain fuel trims in detail? Thanks again.

[@ScannerDanner]

+NG Studios yes you could do that too. Open up the description of this video and you will find a link for a video I've done on understanding st and lt fuel trim

[@miguel1waterpolo1guy]

is anything different in checking the vacuum leaks when the trim numbers is negative? both of mine are negative, what should it do

[@ScannerDanner]

+Universe's rabbithole negative fuel trim numbers indicate a rich condition. So you do not have a vacuum leak on your car. There are many causes for this condition . It would help to know what you're working on

[@miguel1waterpolo1guy]

+ScannerDanner mmm ok. I working on my 99 honda prelude. i just refurbished the alternator and the battery is also new (few months older than the alternator.) when I check the power voltages the battery was around 13.5 static and when I turn on the car jumps to 16 ish. the rmp when idle is around 600-700. I think I can lower that to 500 with the throttle body adjustment thing, should I lower the rpms? what's happening is sometimes when I cold start the engine rpms loop on a jumping rpm.

[@Eddythe_Eagle]

I have the same prob;rm with my 2010 Elantra 4 door Sedan, with a rough idle, poor gas mileage and a performance problem. I hope you get a answer. I did post this problem today, hoping to get a answer. STFT and LTFT both negative but do add up to less that 10% negative?

[@ahmedshamy5315]

perfect Paul, but we can not access to your class because it is not available in our country ...!!!

[@ScannerDanner]

+Ahmed Shamy the link I posted for understanding fuel trim is not on my premium channel. Also I have people successfully gaining access using a VPN. Hope that helps. Thanks

[@edwardthayer9386]

I drove again today another 125.1 miles and the o2s monitor isn't ready. I'm past inspection date so I'd greatly appreciate your thoughts on this. I've never has a o2s monitor not complete this long. And especially be the only monitor to not complete! Thanks again and take care.

[@ScannerDanner]

Thermostat may be opening too soon running the engine at a lower than normal temperature. I've seen this before. What is your engine temp at highway speeds on the scan tool?

[@edwardthayer9386]

@@ScannerDanner ECT at 65mph is 185.0

[@MC-hs4mf]

LT -11.7 , short term 1.6 Bank 2 LT -9.4 and short 0.0 Both long term are negative numbers

[@armang10]

Hi! I have a similiar situation. Were you able to find the cause of it?

[@mikeb5981]

I’m having issues on my 04 ranger 3.0 short term fuel trim and long term on bank 2 reads high at idle and with rpms up. Rpms at idle are 687 to 732. Replaced fuel injectors, spark plugs, MAF, ignition coil, bank 2 O2 sensors, pcv valve, did a smoke test nothing. Any suggestions?

[@ScannerDanner]

What are your bank 1 and bank 2 numbers (need both)

[@mikeb5981]

@@ScannerDanner bank 1short term 3.9%long term 1%. Bank 2 short term and long term both 25% positive

[@mikeb5981]

@@ScannerDanner thank you and God bless🙏

[@ScannerDanner]

@@mikeb5981 do you have a misfire on bank 2? How does it run before it goes into closed loop (before the O2 sensors become active), compared to after? Can you add propane to the intake and drive the bank 2 O2 rich? What is the bank 2 O2 sensor doing during the +25% ST and LT fuel trim. It doesn't matter that the O2 is new. Let's put that aside for a minute.

[@mikeb5981]

@@ScannerDanner I will have to get back with you on those readings it’s been raining so I haven’t been able to do anything to it.

[@edwardthayer9386]

Hey Scanner, I'm having an issue I'd greatly appreciate your thoughts on. It's a 2012 Hyundai sonata 2.4l. At idle stft stays pretty much around 0.0 and ltft stays around 10.2. If I give it any throttle the stft shoots up to 18.0 and the Ltft instantly goes to 0.0 until I let of the throttle. And help and your time will be greatly appreciated! Thank you.

[@ScannerDanner]

MAF sensor or fuel psi issue

[@edwardthayer9386]

@@ScannerDanner it doesn't have a MAF, only a MAP and it's readings are perfect. It's a GDI engine and the fuel pressure is perfect. Sorry my original post for some reason didn't have everything I wrote. My car is past inspection and I can't get it through because the o2S Monitor will not get ready. All other monitors are ready except o2S. I have over 4 drive cycles and 200 miles. What would cause just the o2s monitor to not set. Fuses are all good. I've never had anything like this happen and o2s monitor has always set pretty early for me.

[@rankgts3962]

I’m getting the long fuel trim 0.0 always!!

[@rankgts3962]

I think its the o2 sensor in front

[@ScannerDanner]

@@rankgts3962 monitors not setting is a major pain on some cars and fortunately for me I am not the one that has to deal with that issue. Something to think about is the thermostat, I have seen one that is opening too soon cause monitors not to run

[@thelostmachine8395]

You have a good eye... high dollar scanner, smoke machine to find a disconnected vent hose staring you right in the face. Did you skip the visual inspection?

[@ScannerDanner]

Feel better about yourself now?

[@thelostmachine8395]

@@ScannerDanner : lolz, good show brother, bravo :D

[@phillipzan2005]

Two questions will u see the negitve fuel trim numbers on every vehicle or is that just a GM thing. Second what smoke machines do u recommend a tech looks into for himself, not a big shop one but a personal one.

[@ScannerDanner]

Every vehicle. And as far as a smoke machine goes any smoke is better than no smoke. You get what you pay for if you know what I mean.

[@phillipzan2005]

Soo to have a good smoke machine I have to pay 3000 vs 1000?

[@ScannerDanner]

I've only used two smoke machines. This one and one called redline (I think). So I really don't have much experience to what else is out there. There are guys making there own. Look into it. Do your homework. Sorry that's all I can offer.

[@phillipzan2005]

+ScannerDanner okay I can live with that answer. I had been looking into a littlw I just didntbwant to pay snap on 3k if I can pay1k for the same thing. but thank u I'll be getting one this week

[@bobbybudd2248]

+phillip zanders I bought a disco smoke machine and made some minor adjustments and this worked quite well for me.. Extremely cheap too:)

[@mowglilp]

I thought the STFT should be closed to 0, jumping between negative and positive, like O2 sensors do. At least on BMWs

[@bobbybudd2248]

Hey Paul. If the customer continues to drive the car will the fault code still be stored in memory or will it eventually erase itself?

[@DENicholsAutoBravado]

+Bobby Budd Exactly what I was wondering. For other codes I've seen them stay even though they had no reason to stick around. I've lost pending codes, but not hard codes where the PCM is sure.

[@ScannerDanner]

OBDII mandates say that the fault will erased from memory after 40-80 warm up and drive cycles with no fault. So the average driver would have 2 of those per day (on the way to work and the way home).

[@DENicholsAutoBravado]

ScannerDanner Awesome answer. Thanks!

[@macknumber9]

My short term is -3 and my long term is +7 at times. I don't get why they move in opposite directions. Short term is taking away fuel and long term simultaneously is adding fuel.

[@ScannerDanner]

STFT will have about a 5% swing, it is not fixed. Both of those numbers sound fine. What are you chasing?

[@macknumber9]

@@ScannerDanner Intermittent misfire at idle or at least I think it is a misfire. I get these shakes felt in floorpan/seat...no change really in rpms when it happens so I am actually starting to think it could just be mounts but the weird thing is I don't feel it as much in drive ...I would think i would feel it MORE in drive if it were an engine mount...and it is intermittent not consistent. I did notice some scratches in the coil. I don't know if it is carbon tracking but it is in the housing where the coil towers are. It is a waste spark system. I pulled plugs and I definitely don't have any dead cylinders but I have what I feel like could possibly be a bad coil that is intermittently not firing or perhaps spark plug that is fouled with oil ...I replaced plugs and noticed oil on threads....

[@macknumber9]

@@ScannerDanner I know it isn't fixed but I was just surprised to see long term at +7 and short term down at -3....

[@nicorallysport]

short term and long term, you have to be closest to 0 that's it?

[@vencentbauer]

alot of time my fuel trims long might be 5 and short might be -2 or 3. so that is a good fuel trims 3.8 town and country

[@ScannerDanner]

+Vencent Bauer yes

[@wtbm123]

Nice smoke machine .

[@vencentbauer]

how much was that smoke machine

[@johnmckamy6398]

the maf is 4.43 instead of 3.49

[@edwardthayer9386]

So would you do at this point? Just tell the customer or class that you are unable to fix the car? And that they would have to take it somewhere else or tell the class next car, sorry guys we can't fix this one? I'm really surprised you'd do something like that! Or that you wouldn't want to find out what this problem is! If it's money you want I'm cool with that, I have PayPal. I will even send it first. I just really trusted your advice, I'm totally shocked now.

[@ScannerDanner]

I have no idea what you are talking about. I need some context please. Is this comment in response to a conversation we were already having? If so, please stay in that conversation and I'll do my best to reply.

[@ScannerDanner]

oh okay, I got it now. The way KZbin directs me to these comments is not what you guys see. And you keep starting new threads. Please stay in this one from this point on. When you are answering hundreds of these, it get's confusion. Anyway, you are now talking with me like I am somehow doing you a disservice. You are not my customer, and more importantly, I cannot even see your car! The fact that you think that paying me would somehow get you a better answer, shows how little you know about me. I don't want your money and I've given you my only suggestions I know as to why those monitors won't run. There may be some type of reprogram that needs to be done, but again, without seeing the car myself and doing the research based on the VIN number etc. I have no idea. So your comparison to me just brushing off a customer and saying oh well, take it somewhere else is completely unfair. I will remind you again, I am offering you FREE help over the internet and I have given you what I can, and yet you complain to me about it? What are you shocked about? That I don't have all the answers to all the problems, at the drop of a hat, with all the cars on the road? You have to cut me some slack man.

[@edwardthayer9386]

@@ScannerDanner sorry I just saw this post after I responded to the other one. I will stay with the other one if you choose to help me. I hope you read the other one. I just want to awnser your question to hopefully clear up the situation. First and foremost I'm not trying to give you a hard time, but what I was shocked about is I asked you to sincerely help me with something, not because it was FREE (and you say I must not know you, you're right I don't but what I've gathered from YEARS of your videos that one you're a great tech, sincerely a good person, two it's not about the money) I was just putting that out there so you'd know where I was coming from and that I RESPECTED your abilities and knowledge first! I could have reached out to ALOT of people but I reached out to you because I believe I could trust you that much! I maybe jumped the gun a little early but I didn't think you were going to say change the thermostat WHICH I DID ANYWAY! I didn't give you no shit. I reported back that I did and asked what I could do next. Being super appreciative of your time and knowledge. I was shocked when you said "That's it, that's all I got" I know you didn't say it this way but I felt like you were saying oh well now beat it. I was hoping and thought you'd ask what my fuel trims were or ANYTHING to help me out. I can only imagine all the questions you get! ECSPECIALLY stupid ass shit that is wasting your time or just nonsense. I know you know nothing about me but you remind of myself but just with ALOT more talent and knowledge. I changed the the transmission filter and fluid with oem stuff on a good customer's car today. She hung out and spent time with my dog. It took over 2 hours. When she asked how much do I owe you? I I told her a hundred bucks. She said absolutely not! And put 2 hundred and 50 dollars on my box. I could see you doing the same thing. I surely hope I've cleared up any negative thoughts with my 2 latest responses. If you'll continue to help I'll stay to just one thread or whatever they are called. I'd really like to get this straightened out for her, I'm not getting paid for it. I want to do what I believe is right. I also want to know what's really going on with this car. It's frustrating. I'd hate to let her or myself down ! And you actually if I couldn't get it fixed with your help. Which I know I could. That's why I'm willing to do whatever you say, plus be very thankful for your time and help in anyway that is acceptable to you. Have a great week and I hope you're doing alright with this virus mess going on. I don't have any family, just me and my dog. But I think about the others that it's really affecting and it sucks. I'm doing the best I can by helping my customers with the best service I can provide. Thanks again Scanner, take care.

[@ScannerDanner]

@@edwardthayer9386 agree, text on a screen for this type of conversation is absolutely horrible. I want you to know that I truly do not have an answer beyond what I have given you already. When garages call me and ask the same question, I just tell them to drive it, and make sure the thermostat is not opening too soon. I have fortunately been able to avoid having to do drive cycles myself over the past 19 years of teaching instead of being in the shop. It may have seemed like I just brushed you off, but I didn't, I really just did not have another answer for you. Behind the scenes I am answering hundreds of these every week, not to mention email and my premium member questions and when something requires research on my part to be able to answer specific questions, I have no choice but to direct them to my forum. I just can't get through these messages otherwise. I hope that helps explain my original reply. Sorry you felt slighted by that, I understand why, and you being a long time follower, that probably stung a little. I apologize, seriously, that was not my intent. My forum is free BTW and I have paid moderators who are there to help me help you guys. So I would suggest doing this for you, for where we are right now. Maybe one of my guys will have an answer for you. The community is 17k global members right now, so you'll have a good chance at someone giving you a tip. I appreciate your time and your longtime support. Let me know what you find is the fix okay? Have a great evening.

[@TheBracket1]

Ever run into a STFT rich condition driving ( 20%) then coming to a idle it goes opposite (-19.2%) but LTFT is always 0%? 2000 4runner 3.4 Calif emissions

[@ScannerDanner]

after it is idling for a few, does it recover? what is the LTFT when the STFT recovers to a normal number?

[@TheBracket1]

@@ScannerDanner LTFT always zero no matter what

[@ScannerDanner]

@@TheBracket1 and the rest?

[@TheBracket1]

@@ScannerDanner driving at 55 stft is -20% ltft is sitting at 0%... come to a stop stft will go to +19.2% and ltft will stay at 0%

[@ScannerDanner]

@@TheBracket1 sorry, you said this in the beginning. Unfortunately I don't see these full threads in my email when I reply. A positive trim at idle only, is almost always a vacuum leak. I believe you may have two conditions, with this being one of them. The rich under load, I would focus on the MAF sensor and then perform an injector balance test and make sure they all have the same flow rate. Toyota's had injector issues, not sure about your specific model though.

[@mase202]

hi does anyone know what it means if i have a stft b1 s2 (%) NA and a stft b2 s2 (%) NA ? Hope someone can clarify this for me thanks.

[@ScannerDanner]

s2 is a downstream oxygen sensor and NA means your car does NOT adjust fuel trim based on the downstream O2 sensors.

[@mase202]

ScannerDanner thanks so its not a error reading? thats how it should show ? thanks for your time

[@tracycolorado]

no mention of the brand of smoke machine

[@TheBattlestorm]

snap on

[@tracycolorado]

TheBattlestorm Thank You , there are so many smoke machines where people are not pleased with the output

[@ScannerDanner]

Snap-on. If you pause the video you can get the info you need. Sorry about that

[@sara78130]

i dont now how red fuel trim

[@ScannerDanner]

+KURDISTAN uk you're on my premium channel now, so check out my section 4 and 5 lectures okay?

[@sara78130]

ok thnx