System Too Lean (P0171, P0174) - Vacuum Leak Quick Test - Ford 5.4

This is a Ford Expedition 5.4 with a vacuum leak causing "System Too Lean" trouble codes P0171 and P0174. In this video I will show you how to use freeze frame data and fuel trim numbers to identify a vacuum leak. Then I will be using water to locate the specific area of the vacuum leak.
Engine Performance Diagnostics chapter 1 pages 9-12
Symptoms:
- rough idle
- poor gas milage
- check engine light (P0171, P0174)
- hesitation
- misfire
- runs better with engine warm
Fix
- replace leaking intake manifold gasket
Tests shown
- how to use freeze frame data to identify the type of lean condition
- how to read and interpret STFT and LTFT numbers
- how to locate a vacuum leak with water
- how to locate a vacuum leak with a smoke machine
Tools used
- global OBD-II scan tool
- water bottle
Playlist
- (Chapter 1) Misfire ID, Compression Tests, Vacuum Leaks, Fuel Trim, Head Gasket, Restricted Exhaust, Low Power, DMM
• (Chapter 1) Misfire ID...
Related videos
- Understanding Short Term and Long Term Fuel Trim (an SD Premium video)
• Understanding Short Te...
- Causes of lean condition trouble codes P0171, P0174 - GM 5 3L
• Causes of lean conditi...
- P0507 Idle Speed Performance Higher Than Expected (vacuum leak) - Jeep
• P0507 Idle Speed Perfo...
- Ford F-150 P0171 P0174 Trouble Codes - vacuum leak (water test)
• Ford F-150 P0171 P0174...
- How to find a vacuum leak with water
• How to find a vacuum l...
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.
Want even more diagnostic training? Whether you are a DIY trying to fix your own car, someone looking to become an auto technician, or a current auto technician that wants to get more into diagnostics, subscribe to ScannerDanner Premium www.scannerdanner.com/join-sc... There is a 14 day free trial.
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.

[@maxwelltengbeh2894]

Very good. The smook test was also helpful.

[@roadracingmustang]

The 4.6 in my 03 F150 had the PCV hose connection behind the manifold crumbling. It is a real bugger to change and can't be seen from the front or side at all. Replacing it cured the P0171 and P0174 codes on mine.

[@feeneysmechanical6215]

Thank you again Paul for a great video.

[@wyattoneable]

I'm back from vacation and just enjoyed this short video. I want to catch up on some newer case studies then I'll get back into some lessons. It's good to be back.

[@rrmech11]

Glad to be back to watch your videos Paul. Been following you for years now.

[@ScannerDanner]

+Richard Gill everything okay?

[@fieldsofomagh]

The trims and elevated speed give a good indication of a leak and fast.

[@arielcastro538]

Dude, Great video. I'm going to try this right now. Thanks

[@joevignolor4u949]

The 3.8 Liter V-6 in my Windstar threw the same two trouble codes. Apparently it's a common problem with that engine. It's caused by a defect in the material used to make the grommets on the isolator bolts that hold the intake plenum onto the intake manifold. Replacing the isolator bolts solves the problem and it's easy to replace them. A lot easier that replacing the intake manifold gaskets on the engine in the video.

[@MrNellayort]

Nice water test dude brilliant and simple

[@mtrltoolman]

amazing short video thank you.

[@wtbm123]

The water test is a good one , i use it a lot now

[@traxiii]

Had those codes on my 2001 and found the grommet for the Air Charge Temp. sensor had deteriorated enough that the sensor was sort of falling out and the grommet was no longer keeping air from entering the air tube. Probably the easiest thing it could have been. The hardest part after that, was finding a new grommet the right size.

[@tomduncan1970]

This is totally ironic. I just watched your other video (F150 vac leak) LAST NIGHT because I am pulling 2 does on my 2001 Navigator. P0171 & P0174. Thanks Dan!

[@isaacd5845]

Did this work for you? The water

[@Affordablebath_remodel]

well done video. clear sound, very good at explaining.

[@ScannerDanner]

thanks so much!

[@thomasconklin4873]

tom c. very heipful, I'm going to try it. thanks

[@andreagili4589]

Super video Paul ! I haven't had the opportunity to troubleshoot ad intake leak just yet, my water sprayer twitches :)

[@ScannerDanner]

+Andrea Gili haha

[@freddysoto6584]

Havent even watched cideo but I know its a good piece.

[@LetsFixIT]

I lve your videos , another great one.

[@noelconroy3647]

Great video thanks for sharing :)

[@Autofixpals]

do I hear idler or belt tensioner pulley bearings screaming?

[@bigbassaholic9478]

Great video bro. I'ma try to fix it my self i have had this light on for about a year so i have to fix it before my next smoke test. Like you said it. Fords like to get this things eat up. Lol.

[@cookdave]

Do you run any risks by spraying water into the engine bay?

[@thomasv5596]

a gentleman and a scholar

[@sablan02]

Hey Paul! This is an off topic suggestion, but you think you can do a video showing your electrical test equipment such as scanners, meters, types of leads, probes, etc..? Would like some recommendations. Thanks!

[@salemogla1495]

hi pual is this video accompanied with the sixth edition of your book Engine Performance Diagnostics or not because i haven't in my copy of this book

[@freddesgarage]

Hi Mr.Paul! i am working in a -98 volvo v70.i can not find a wiring diagram for it.should the purge solenoid be fed with 12 v or is it a good number 6v that i have?is it fed by the pcm? hope you understand me 😆 hope to hear from you//

[@micsor4121]

supper thanks again. may your Blessings be high octane!

[@brianwurks]

great tip but sure you wouldn't be shorting the coils most common for those codes is a pcv valve tube regardless love you vids tips and tricks definitely a fan keep em coming Dan

[@johnmckamy6398]

I like that little tool can you put a link or information about it . thank you for everything you do for us

[@DENicholsAutoBravado]

On small leaks I've found brake clean and live data helps. When the STFT consistently goes rich, you've found the leak. Leaks too small for those methods? Smoke or like a video of mine where I went crazy DIY with no fancy technique, just look for and replace crusty vacuum lines.

[@ScannerDanner]

+DE “AutoBravado” Nichols used that method many times myself

[@mitchelhibbard1220]

I've got a couple of cylinder misfires. With the P0171 and P0174 are the only codes I get off my OBD2. The intake manifold gasket has been replaced before. Will those codes if not fixed end up constantly misfiring? Also I normally get my parts from Amazon, and the isolator bolts the try to sell with the gasket set doesn't fit my truck. It is a F-150 4.2 2001 model.

[@kchilz32]

would a bad intake manifold cause smoke to come out of the tail pipe for a few minutes when starting a 2000 Ford F-150 5.4l? Thanks.

[@noelmatute5977]

l really enjoyed video thank you matute

[@marvincheever5124]

Hay Paul this is Marvin I would like to see more uses with the scope.

[@carslover3509]

great master

[@dbbias1416]

Thank you, water bottle is great 👍💯

[@ahill007ny]

Nice review of the water technique! That is the same scan tool I use :)

[@byranguy4638]

great video scanner danner watch all your videos very interesting hoping if you can help me with my 02 explorer have lean trouble codes have done everything to it smoke the car to find any leaks and find my egr smoking like crazy replaced it and still have trouble codes thanks

[@68dippin3]

Thanks for the reply I did a fuel pressure test it reads 30 33 PSI then with the brake on I put it on Drive it reads the same 30 33 PSI I put it back in park rev the engine up it almost hits 40 PSI is this normal?

[@weegocamargo1883]

are you not worried about water getting to the coils

[@Pablo_Automotive]

Nice video¡¡

[@oSTYNCLSYo]

06 range rover HSE 4.4l with code p0171 only. Any idea what might be the problem?

[@crex7395]

MUST READ! I was going crazy trying to get that error code fixed. I have a 03 v6 4.2 and turns out the leak came from bolt bushings at passenger side intake lower portion. Ford released a service bulletin TSB 04-17-04. Hope this helps for anyone who struggled as much as I did.

[@miketheasswaxer6814]

!

[@matadaniel]

what is a service bulletin

[@scottskinner577]

@@matadaniel its like an advisory they send out for technicians to be aware of

[@j06c]

my SFTRIM went to 41 when i rev it up. is a vacum leak?

[@turboflush]

Help.. I got the same codes.. 2008 expedition 5.4. High Ltft's don't change on higher rpm. Checked MAF signal ok. Swapped it for s&g. As far as I can tell.. no vac leak. My cheap scanner does a horrible job looking at the o2's. Any suggestions?

[@williamcolantuoni4503]

Smoke machine definitely. H2O+ Ford COP=misfire!

[@mariobortoluzzi2929]

QUESTION: Would using starting fluid and shooting it around the intake also work? When the idle would change you most likely have found the leak, correct?

[@ScannerDanner]

This is a MAJOR fire hazard and I do not endorse this method. IF you are going to use a fuel source to find a vacuum leak, you need to be aware of the hazards. (intake back fires can occur, igniting the fuel, spark plug wires and coils can leak and ignite the fuel)

[@mariobortoluzzi2929]

Concern NOTED! Thank you!

[@Case_]

If I may ask a quick question related to vacuum leaks and testing them - can a MAP based engine with fuel trims that indicate vacuum leak (as in they get better on higher rpms) still suffer from a vacuum leak when the MAP sensor is showing normal intake vacuum (well, as far as I can guess - don't have specs available) and the IAC is not fully closed yet? I would kinda expect the vacuum to be lower under such circumstances - why wouldn't the ECU just close the IAC more instead of raising the fuel trims or MAP show lower pressure than there should be? I've been struggling to find a leak for weeks (on and off), but with no amount of carb cleaner or water spraying I seem to be able to find one. Yet the fuel trims seem to point to one. Also, I think I can kinda hear some hissing close to throttle body, but again, no dice on finding a leak, so I'm wondering if what I hear is simply the hiss of air running through the throttle body/IAC that's supposed to be there...? Thanks for any advice.

[@ScannerDanner]

what kind of car? if it has a plastic intake, they are noisy and hiss and sound like vacuum leaks but it is just the intake

[@Case_]

Thanks for the response, much appreciated. It's a 2002 Ford Focus (European) and it does indeed have plastic intake (it's a 1.6 Zetec SE). Didn't want to bother you with details on what was supposed to be a fairly general question. I'm kinda wondering if the elusive vacuum leak - which doesn't seem all that big, if it actually is one - could in fact be caused by leaking throttle plate since there really doesn't seem to be any vacuum leak I could find and I know for a fact the throttle plate isn't exactly sealed. But all that aside, I just don't understand why I'm seeing positive trims when MAP sensor seems to be working fine and reading normal vacuum with IAC also seemingly active and working properly (reads around 31-33 percent open at idle). I'd kinda expect to see one or the other on a MAP engine with a vacuum leak (meaning positive trims at low rpms or normal MAP/IAC readings), but not both at the same time. I can't understand why the ECU would raise trims instead of simply closing the IAC more to compensate for the air coming in through the leak - unless I'm missing something in my understanding of how it all works together (which I guess is quite likely).

[@Case_]

BTW, still struggling with that lean idle condition, still can't find the reason. No vacuum leak in sight. It kinda seems to me that the lean idle condition is dependent on intake air temperature - the higher it is, the higher the trim numbers (and the worse the car runs at low rpms). If I unplug the MAP sensor (or TMAP, to be precise), the car idles just fine, the STFT basically cancels out the LTFT (the overall trim is around 3 %, so perfectly fine), the O2 does seem to cycle up and down fine (definitely not suggesting a lean condition). The only thing that's off when I unplug the MAP is that the idle gets a bit higher (around 150 rpm more than normal) - but then again the IAC is also open a few percent more for some reason, so it might be that. Could this perhaps suggest the TMAP is somewhat out of calibration at lower vacuum/higher temperature, causing the ECU to run on leaner base values than it should and having to compensate the offset with higher fuel trim? Or is unplugging the MAP sensor a meaningless test?

[@Case_]

So, to finally follow up on this for anyone who happens to stumble upon it in the future (because I hate when people don't follow up) - I believe the issue is finally solved. Even though it exhibited all of the classic symptoms of a vacuum leak, it was actually a MAP sensor off calibration that was causing my lean idle (which I guess makes sense, as my engine is a speed density engine, so it depends on accurate MAP reading, but shouldn't really show higher fuel trims with a vacuum leak like a MAF engine would). Apparently it was reading more or less correct at barometric pressure, but as the pressure decreased, the calibration error was gradually increasing, mimicking the classic vacuum leak symptoms. It was off by something like 5 kPa at idle and even more when e.g. engine braking. So it was kind of a pain to diagnose. Replaced the MAP and the highest fuel trims I've seen so far was like 7 percent overall, which is a LOT better than my previous 25+ (STFT and LTFT combined). I was also experiencing quite a lot of engine knock under light acceleration, and that seems to be a lot better as well overall. So I guess the answer to what can cause a vacuum leak-like fuel trims on a speed density engine is - it might very well be your MAP sensor.

[@scottgrippo4173]

@@Case_ thanks for all the info!

[@steventenney8797]

engine running at 20 inch vacuum is the same force on the sealing surface as 10psi net pressure. im sure the smoke machine only uses inch WC.

[@ScannerDanner]

+Steven Tenney good tip Steven. Thanks!

[@jquiznos2283]

How much should it cost me to take it to a shop and have them tell me this same thing? I have 4 codes and I don't have the energy or a smoke machine to figure this out.

[@mohamedelshamy2706]

Hi Paul, I made my first video. thanks.

[@rob_v_nj]

My 2000 5.4 2 valve 157,000 had bad cold rough idle, as you say high fuel trims and when real cold the P0171 P0174. Would clear up as it heated up. Tried to smoke it cold and nothing showed up. First I pulled throttle body off to clean and check that upper gasket as well as all of the vacuum hoses. Put back together, same thing. I should have done this water test but i knew that it was gaskets, common issue due to dissimilar materials plastic intake and aluminum head. I ordered the good Felpro gaskets and when pulled intake saw the dreaded crossover coolant crack as well as gasket separated. Order new Ford intake via amazon as well as motorcraft injector o rings. #7 COP sucks to get out. Had trouble disconnecting the fuel lines with my cheap disconnect plastic rings but i eventually got it after 20 minutes or wrestling. Thing runs like a champ.

[@rob_v_nj]

Was the intake gasket , had plastic intake with coolant crossover crack. Installed new gaskets and ford intake. New injector o rings and cleaned the injectors

[@scottykilmer1094]

This guy is my favorite !

[@Warren1814]

What is you have both codes PO171 & PO174 and you car / truck still runs fine.... (At least for now it runs fine anyway) At high rpms and at idle I drink a 2000 ford e150 van I really don't have the money $450 - $750 to get it fixed right now. is it safe to continue to drive it? (i'm in a wheelchair and i can't fix any of it myself unfortunately )

[@thatsubae]

What's the desired fuel trim numbers for this truck?

[@malachifine24]

idek '

[@raycook1503]

I always did brake cleaner and watched fuel trims change as I spray around hoses and intake.

[@ScannerDanner]

I used to use a flammable source until I had an intake backfire and caught the engine on fire in front of a customer 😅

[@w8up4rick98]

Scanner Danner do u have an email or anywhere to ask you questions that aren't related to any specific video's. I'm trying to get more involved in diagnostics and would like to purchase some equipment but don't want to put my money in the wrong place.

[@ScannerDanner]

+Rick Waite Post these questions to my forum on www.scannerdanner.com Thanks!

[@kevinarmstrong4815]

currently trying to diag a 99 ford expidition 5.4 sat for a year car came in for a p0171 code, not sure what the last tech did but when I got it long term trims at idle cold engine around 13% (bank 1 and bank 2) driving it i see bank 1 jumps to about 20% bank 2 stays around 10% I have smoked it found a vacuum leak, repaired it but no change. I will try this water trick tomorrow when I go back to work

[@ScannerDanner]

So trims get worse at higher RPM? That's not a vacuum leak symptom

[@shay5129]

What should the short term fuel trim numbers be at idle and higher RPMs?

[@ScannerDanner]

+Shay “PoorBoy” Linton they should be hovering around 0%. Watch this video, it will help kzbin.info/www/bejne/pYO7Y4lslMZmmsU

[@joseph2323]

short 7.8 long 9.4 trim.. what does this mean ??

[@juanreyesalarcon9164]

I have a vacuum leak but It doesn't show those codes. It only shows misfire in all the cylinders even after replaced coils and spark plugs. Any ideas? 06 rendezvous 3.6L

[@Mike-01234]

those 5.4's have the deep spark plug water gets down in the coil and shorts had this happen after washing my engine had to remove the coils and boots blow it all out let it dry overnight.

[@mattbraga4033]

So what if your trim numbers didnt improve at 2500 rpms? What would that suggest?

[@ScannerDanner]

Fuel pressure too low or MAF sensor issue or your two most common issues

[@raybradley1502]

nice, mine was cracked t connection

[@joseph2323]

freeze frame.. mine says idle rpms 2400 no matter what .. i rev and do test over and same rpms .. how do I change freeze frame ? everyday says the same n I only have.freze frame on tool

[@stevenpo1963]

Water short out the spark plugs and change engine sound I use carb clearer my great uncle used water and oil to seal in old days

[@IsshmanGarcia]

so Paul, I just completed the PARKED fuel trim test. You asked what the Ft rims look like @3000rpm PARKED. The results are as follows: With the car fully warmed up at idle and parked= idle 725, LTFT 14.1-11.7, STFT 2.3-1.6 /// CA IN PARK @IDLE & 3000 Rpm= LTFT 16.4-10.9 , STFT 4.7-0. NOTE: WHEN THE LTFT REACHED 16.4, THE STFT WAS AT 0 THE WHOLE TIME. Once I let off the throttle they basically when back to the approximate readings as they were. Any suggestions?

[@IsshmanGarcia]

CORRECTION: the "4.7-0" from the actual test was a (negative) -4.7 NOT positive!

[@ScannerDanner]

+Isshman Garcia you need to stay within the same conversation because I don't remember what the initial complaint was

[@IsshmanGarcia]

+ScannerDanner sorry I'll repost

[@miltonscornertobylove5068]

Sweetttttt.

[@greengoblinkush1404]

can you damage an EGR valve by cleaning it with carb cleaner ? i cleaned the one on my expedition and it runs very shitty now ..i put a new egr gasket and the truck smells like fuel , i had a p0171 -174 code before i tried cleaning it ..

[@ScannerDanner]

I don't think so, unless you were spraying it in the diaphragm area

[@rotcataergeht]

I have negative LT fuel trim at idle for both banks, and also negative fuel trim at 3000rpm both banks. V6 engine. Rx330. Is this vacuum leak.

[@mikhailkurylenak1515]

you running reach, means you got too much fuel or not enough air. Could be many reasons, i d check maf sensor and fuel system first

[@Ezzell_]

@scannerdanner do you have a link discussing trim data and how to understand it?

[@ScannerDanner]

+ken ezzell sure do. Here you go kzbin.info/www/bejne/pYO7Y4lslMZmmsU

[@livalittle100]

+ken ezzell Man watch the video he linked. It is so informative, its so well done.

[@themrrd12345]

Hmm my 4.6l 2v mustang has the same codes and going to 2500 rpmz brings the fuel trims only to like 21% any suggestions?

[@davidrowe8771]

O2 or mass airflow if it corrects itself at 2500rmps but goes back to 20 at idle then it’s a vacuum if it’s close to 0 at idle and goes to 20 at 2500 rpms will be mass air flow or o2

[@ethanwright3626]

How do you pinpoint the vacuum leak tho?

[@jamesvoth3648]

I've got a lean condition P0171 and P0174 with the O2 sensors voltages looking good but the short term fuel trims on both banks second sensors reading at 99.2%. It's a 2004 FX4. The reading is so extreme, I don't know where to start. Any Ideas?

[@ScannerDanner]

+James Voth The second sensor is downstream and the fuel trim numbers are not used for downstream O2s on your Truck. The 99% reading you see is a bs number and means nothing Focus on your upstream fuel trim numbers

[@jamesvoth3648]

Thanks for your reply! Very much appreciated.

[@joeychaseable]

@ScannerDanner I've got a PO174 on my 03 Expedition. I've got pics of the freeze frame data from my scan tool. I've checked for intake leaks with no luck. Mine does not get better or worse when warm. If the truck is driven in "normal easy manner" it's hard to notice any problem. Occasionally at a stop light I'll feel a little hickup. Problem occurs under any kind of load. it just won't go. 1/4 throttle going down the road, it simply is hard to get rpms over 2,000 and to get it going. I'd love it if you get the time if I could email you pictures of the freeze frame data and if you could maybe brake the "code" of my issue. Any help would be great! Thanks, Stan...

[@josephpurcell3341]

Did you figure it out? Im having same issue on my 03 gt

[@AntoineFinch]

can that cause smoke after highway travel? coming off engine!

[@ScannerDanner]

no, smoke coming off of an engine is either coolant, oil or fuel

[@bbhjcds]

Ur intake gasket is leaking Pete!!!

[@fuzzyfish80549]

My concern is getting the smack shocked out of me by stray secondary voltage. What's the chances?

[@ScannerDanner]

As long as you don't have a pace maker, you'll be totally fine

[@SufyanKhan-qu8bv]

I am getting code P0171, i have checked all leaks , the shorterm fuel trim is 46.88% , long term fuel trim 18.45%. Air fuel ratio 26.75 , O2S1 -3.5mA, O2S2 is 0.9V ,

[@Asad-NBT]

Which car is this?.... Did you monitor short and long term fuel trims at idle and when you increase rpm.... How they react? If they tend to correct themselves, meaning bring the values closer to 0, then it's a vacum leak issue If they don't correct them selves and infact get worse, then the issue is related to fuel delivery or MAF

[@68dippin3]

Hey whats up man ! I have a expedition with 5.4 the truck idles alright litle chaky but not that much when i go and put it in drive it stumbles and almost dies when i put it on revers it complete ly dies and if its in drive and i hit the gas it has no power any help?

[@ScannerDanner]

+68 dippin Can't really help you without more direction. Trouble codes? What is fuel pressure? etc

[@davidmenchaca488]

I have a ford expedition 5.4 2002 model. And my battery started reading H when driving.. High voltage sobi got a new battery cause the battery started smelling ugly like rotten eggs. Put new battery in and still reads high voltage what isbthe problem why its doing that now

[@usagimoto1423]

What did you use to smoke the system as far as vacuum lines?

[@ScannerDanner]

A smoke machine that uses mineral oil as the source

[@usagimoto1423]

@@ScannerDanner ok, I believe mine uses the same but which vacuum line did you attach it to

[@Texnoyley]

красава! чел валит

[@gurlno9007]

Holy Hellacious! Are you kidding me. Bring my truck in this shop with PO174 code. Leave with 174 codes because now all my shit is fried!

[@ScannerDanner]

Lol, water is not going to fry anything. What do you think happens when you drive in the rain?

[@gurlno9007]

@@ScannerDanner let me keep it simple Electrical connections, fuses, poor wiring are all easily damaged by spraying water in an engine compartment this way. Considering the culprit in the video are lean codes, faulty sensor wiring from the PCM, MAF, EGR and any number of pcv valves to bad sensors can create those codes. Spraying them with water can make the problem worse. I guess if you plan on driving though 3 ft of water with no hood then sure a rainstorm would damage your engine.

[@sofian119]

I really like to thank you, your videos are very instructive, I would like to have your opinion about a case, how can you have a lean condition in the long term fuel and a rich one at the same time, meaning in short period . exemple in 2 minute drive the LTF is between min -35 % and max 89% short term fuel between min -100% and max 16% at idling constant LTF -35 , a wave fome STF min -27 max -24 DTC: lean condition Pending Code NB: fuel pump has been changed thank you

[@ScannerDanner]

Fuel trim analysis should be done during a steady throttle. What are your LTFT numbers at idle and 2500 rpm? A test drive is not needed. Just running in park is fine

[@sofian119]

LTFT at idle -35% at 2500 rpm 89%

[@ScannerDanner]

I need both banks

[@sofian119]

there is only one bank, it's vw Golf mk5 1.4

[@ScannerDanner]

I've seen MAF sensor contamination cause a negative number at idle and positive at higher RPMs kzbin.info/www/bejne/eXaum52Og7GHoM0 If you need more help. Post to my forum scannerdanner.com/forum/post-your-repair-questions-here.html VW's have a different way of displaying their trim numbers and if you are using global data, it can be misleading.

[@johnmckamy6398]

I have a 4.6 where I thought that the intake leak but it ended up being the O rings on the injectors leaking vacuum .

[@ScannerDanner]

for sure, another reason I like the water test, you can see it getting sucked in

[@artcontreras9291]

John McKamy for a week had atap noise then it died out when I left work.. hasno power to even get up driveway.. thanks

[@josephpurcell3341]

Would that also cause a light tap sound at idle? I have 03 gt 4.6 soch 2 valve just replaced stock intake manifold with the pp typhoon one and felpro gaskets. Also we put fuel rails on new plugs and serpentine belt. Ran fine first day next day heard light tick near fuel pressure sensor and check engine light is on with same two codes.

[@joeandgod1]

Paul, with all the years you've been in automotive diagnostics, can you please tell me why a simple smoke machine is so damn expensive ? A 1,000 dollars !

[@ScannerDanner]

+joeandgod1 go to my forum, there is a thread there where guys are making their own

[@casperlovesstephie]

scanner Dan I have a f150 2005 5.4 triton. it had a misfire code on the 2 cylinder and a bank 1 lean code. I have replaced all plugs and coils. and misfires went a way for a few and then it was running worse I was checking fuel trims and looked under the car and seen the cat was glowing red. and I disconnected the cat on passenger side and it started running a little better then too. and has power that it didn't before. but know I still have Bank one lean code and it still runs rough. but my fuel trims aren't high and it's saying coil 6 and 7 have problems but I check them and there sparking just fine any ideas Michael

[@casperlovesstephie]

any idea

[@chrisvincent9840]

Michael Starcher I had issue turned To the vacuum on the back on intake manifold 6C324 IIRC,

[@chrisvincent9840]

Michael Starcher 6C324 IIRC, ford part # 30 to 40 at the stealer ship

[@keithperkins1445]

You can also use a mapp gas torch un lit turn gas on and aim tip at locations you suspect leaks if the engine idles up you have a leak there. Much easier than a sprite bottle 😅

[@ScannerDanner]

Water is more accurate in most circumstances

[@bri-manhunter2654]

Can a bad ground wire cause this, or a missing one????

[@ScannerDanner]

a bad ground can do a lot of crazy things for sure, but most likely not with lean codes unless the O2 sensors share this ground you are referring to

[@user-zm1im9gk4y]

Why would You use water instead of carb/choke cleaner? That water will foul the plugs and blow the coils?

[@ScannerDanner]

To prevent a fire!! And it's more of a pinpoint test and no, you won't hurt the engine

[@Mr99RICH99]

very ironic that I'm working on a 2002 expedition 5.4L ...looks like it was pulled from the swamp ......severe misfire and won't go over 45 with no codes ....feels and sounds like it's running on 5 or 6 cylinders

[@MrAnthonyfym]

you have to use a good scan tool that does power ballance

[@masscomnet]

A smoke test is what you need.

[@ScannerDanner]

Not everyone has one, so I showed a way it can be done without it

[@Legal_Addiction]

I've been going though mine, just rebuild the engine last fall. Just replaced the intake gaskets just to rule that out. I've checked hoses, seals everything I've seen online and I can't find it. My ltft doesn't get better as the truck gets warm. I'll have to find a smoke machine.

[@ScannerDanner]

It may not be a vacuum leak. That isn't the only thing that will cause a 171 or 174 cod3

[@Legal_Addiction]

@@ScannerDanner I'm getting a 171. I instead Stage 2 cams, springs and locked the phasers plus 2 different custom tunes. I'm going to try running with live data see what I can find.

[@ScannerDanner]

@@Legal_Addiction when you change components in an engine and add custom tunes, this puts you in an entirely different arena, good luck

[@Legal_Addiction]

@@ScannerDanner yeah you definitely got that right! I appreciate the reply. Have a good day!

[@fuckjewtube69]

I'm trying to diagnose an engine thats running rough and rich. It doesnt have a vacuum leak it passed the smoke test. The problem I ran into is the car is not going into closed loop and I cant check the fuel trims or O2. Any advice? The only code is lean system code and its a MK3 Jetta with a 2.0.

[@ScannerDanner]

+rsx123 without being able to look at trim and O2 numbers, you are not going to be able to fix this car without throwing parts at it. MAF sensor failures are common

[@joevignolor4u949]

+rsx123 - There are Bluetooth devices available that plug into the vehicle's OBD2 port and can be used along with a laptop running applications software that turn the laptop into a scanner. It's fairly inexpensive and quite capable for the money.

[@fuckjewtube69]

Joe Vignolo I'm using a SnapOn scanner provided at work. What I meant by cant check fuel trim and O2 is it doesnt show those pids if its not in closed loop. The car is permanently stuck in open loop.

[@fuckjewtube69]

ScannerDanner I changed the MAF before it started running bad with a used one (cheap people) I figured it was the MAF as well but the guy doesnt want to pay up for a new one. Thanks for responding.

[@joevignolor4u949]

rsx123 - It also sounds like you could have a bad upstream O2 sensor, which would keep the mixture control system in open loop. There are ways of checking the O2 sensor directly even if the scanner won't show you the O2 sensor's output. If your cheep friend keeps driving it running rich like that he's probably going to need a new catalytic converter pretty soon, if not already.

[@williampierce5615]

So it's adding more fuel at idle because it's getting unmetered air.

[@littlemoo52]

mine gets worse. rough idle at stops and wants to buck at around 45 mph. code was P0174 on bank 2 only.

[@cardsfan2321]

PCV valve?

[@IsshmanGarcia]

my ltft is at 14 and st is at 0 at idle..would that suggest intake leak? or could this be a symptom of the 02s and catalytic issue i have as well?

[@IsshmanGarcia]

both fuel trims are normally both positive at initial startup..then they turn to the numbers from above comment once warmed up.

[@ScannerDanner]

+Isshman Garcia what do they look like at 3000 RPM in park?

[@ScannerDanner]

+Isshman Garcia fuel trim numbers during start up is not something I ever look at. O2 sensors are cold, system is in open loop etc. There are some circumstances where a LTFT can affect initial start up fuel control but not typically.

[@IsshmanGarcia]

+ScannerDanner Sorry, when i said startup I was referring to have started up the car and let it idle a 5-10 minutes..NOT during startup as in a relative compression test. If that helps a bit.

[@IsshmanGarcia]

+ScannerDanner Normal trim numbers= idle 725, LTFT 14.1-11.7 , STFT 2.3-1.6 /// Now @ idle and 3000 rpm is as follows= LTFT 16.4-10.9 , STFT -4.7-0 (negative) Once I back off the throttle, the Fuel trims return to the same approximate numbers as the "Normal" data.

[@richlininger4349]

Sounds like it has a bad idler or bearing noise too

[@marvinsolis5166]

Can a vacuum leak cost the transmission to shift funny (help) thanks l have a 2005 f 150

[@ScannerDanner]

any engine running issue can cause the transmission to shift funny, if you know you have a vacuum leak, fix that first