Negative Fuel Trim Indicators | Ron Bilyeu | Tech Tip

[@Aaron-hd8ql]

Thank God for you sir finally someone on KZbin who explains what parts to look at replacing instead of wasting time preaching, it goes up and down in numbers. We all know they go up and down in numbers, but replacing parts is key to diagnosing as well, so thank you for the amazing and knowledge filled video. Now I can go out in my car and start looking at stuff properly. God Bless you, sir.

[@sadaqanihouvi4797]

This is the best explanation I got about Negetive Fuel Trims. Especially the latest information regarding oil contamination. This has been my case 👏👏👏👏👏👏🔥🔥🔥🔥🔥🔥

[@r3alfish]

Omg this dude was a teacher of mine in college and I just found this by accident.

[@michaelrodriguez2920]

Thanks you! Perfect video, straight to the point with 0 fluff!

[@JMUDoc]

Negative trim means 1. over-fuelling - faulty pressure regulator, leaky/faulty injectors 2. under-burning - weak coils, faulty/fouled plugs 3. air blockage - blocked intake or clogged cats (if one cat is blocked, that side will go negative while the other goes positive) 4. faulty sensors - MAF, lambda.

[@sonofsteve566]

well Done! have a v6 reporting -24 shrtrm trim on both Banks/ belive its air. But I never thought about the contaminated oil, This sir opened my Eyes, so, I thank you.

[@caesarforlife1663]

Great explanation that is straight to the point with no BS. 👍

[@AbuDujana692]

Wow great explanation...after so much of KZbin search, I could find this great explanation of reasons behind negative fuel trims...keep it up with the nice work Sir

[@josepeixoto3384]

Thanks to you, i suspected i had a MAP sensor over-reporting engine load,both fuel trims were around minus 20,still no engine light on,it was just a routine check; replaced it with one from another car,i have three(2000 and 2001 daewoo nubira SW 1600 16V--one of the *BEST* cars i´ve seen-35 years as a mechanic-cheap to buy,dual fuel,gas and lpg, 260000 kms, quiet,everything functions like new,nothing breaks down),and now fuel trims are fine.

[@tsazeredo]

Boas, José. Também tenho um Nubira 1.6, mas é Chevrolet e ano 2007, no entanto presumo que o motor não mudou tanto assim. Também tenho essa suspeita que o sensor MAP não esteja funcionando bem. Onde compraste o sensor? Obrigado.

[@giannivalenza1751]

Thankyou so much for your full explanation. After a lambda fail my car was running rich and reporting lean. Changed the lambda sensor the car was going fine but with a 10-15% correction on the lean side. Thanks to your help I've changed oil and oil filter (only 500 miles aged), and everything is back to normal now! I still got a problem of negative LTFT when running on LPG (got a bi-fuel Opel Astra J 1.4 104kw): maybe you've got a clue for that too? I really appreciate your calm and clear explanation!

[@maks1251]

Hey man, did you do antything to get lft with lpg sorted out? im having a similar problem of ltf on lpg being -12%. Opel corsa d

[@giannivalenza1751]

@@maks1251 I've solved changing LPG Injectors. Spring inside comes weak and they start leaking, somebody says even after 50-60kkm. My trim was bad low expecially without load. Now it's clear to me that the root cause was leaking injectors, showing the leak more when commanded pulses are short.

[@maks1251]

@@giannivalenza1751 Thank you for your response. Unfortunately, my lpg instalation has 3k kilometers driven and its a pretty decent kit (tailored to my car by someone i trust), so i have to look somewhere else :/

[@Fcnjesse]

Best video on the subject thank you kindly sir

[@tomaslopez4322]

Very good video! My car is running -9 , i changed both upstream sensors because of a p2a code.my car still hesitates during hard acceleration. I cant figure out what it is

[@tallevi6172]

Thanks a lot, I am now encounter a negative fuel trim and want to fix it

[@ozzstars_cars]

well said, thanks

[@FerasDishli]

Perfect explaining tank you 🙏🏻🙏🏻🙏🏻 Is LTFT should be stable? In my car LTFT are -5 % while driving, But when i release the throttle (gas) pedal then LTFT go down to -13% When i push again throttle (gas) pedal then LTFT back gradually -7% -6 % to -5% and some times -4%. All this problems i have it after i added STP fuel injectors cleaner. I smell fuel in the engines oil and i did change the oil. LTFT should be stable while driving? Or what? Thanks a lot 🙏🏻 Camaro SS 2018

[@AnythingEverythingGh]

Did you fix it ?

[@SuperCarSweden]

@@AnythingEverythingGh It was for a friend’s car ; It was injectors leaking and the LTFT went down to -23% We did change all injectors, and change the oil again The car now runs perfectly If you have injectors leaking then the engine’s oil will smell gas clearly. Check your oil

[@AnythingEverythingGh]

@@SuperCarSweden In my case injectors are good and they are not leaking fuel into the combustion chamber. Don't really what to look up next again; am running rich

[@SuperCarSweden]

@@AnythingEverythingGh What car? What mode have you? Tune? Did engine’s oil smell gasoline? What LTFT have?

[@AnythingEverythingGh]

Nissan Sentra 2008 No tune Yes, engine oil smell gas being running rich for long Check map sensor, injectors, o2 sensors, air filter, fuel pump, spark plugs, even changed Pcm/ ecm too No changes Btw, when I remove the engine oil dipstick while watching fuel trims, the ltft reduce a bit to about -8 instead of constant-10.6 whiles stft oscilate between -20 > -3

[@BigAlWillis]

excellent info - thumbs up

[@muslim_ontop]

Salute good explanation

[@timhanson8335]

Absolute best video ever

[@ufuomaemefe8173]

Thanks for your video.pls have Toyota RAV4 2010.i am have negetive-7.steding.what will be the causes.my car is consuming more fuel.

[@Destructive_Asylum_13]

Hi I have been chasing p1137 code for month. Vw 2001 vr6 I have put new maf, injectors, fpr, purge valve , o2 & sill keep getting -14 LTFT ANY IDEAS please. Thank you.

[@slowazbmwkilla3073]

Great info with a ton of facts

[@231057jorge]

Hello, I have a 10 TSX 2.4L both my Fuel Trims are negative (-18%) I got a new dense upper sensor, if i disconnect the upper 02 sensor the short term goes back to 0 (which makes me believe injectors are fine and no air leaks ) if i plug the upper o2 back in it goes back to negative. after driving it for 10 miles i get a p0420. ANY IDEAS ? THANKS

[@AnythingEverythingGh]

What about boost leak, can that cause negative trim too?

[@cimmet1371]

I have never worked with turbos really but if you lose air that has been messured by the maf ex. maf read 10g/s but the combustion only gets 7g/s then your car should run rich yes

[@kumars172]

can u explain what boost leak is?

[@johnjauregui3528]

How does ethanol affect ECM/PCM fuel trim calculations? Does it require the same 14.7:1 ratio calculations or some other ratio? If so does the ECM/PCM sense whether the fuel is ethanol or gasoline and use a different ratio for ethanol? If the ECM/PCM assume gasoline is used and does not adjust for the use of ethanol what is the impact on air/fuel calculations and fuel trim outputs? How does this affect scanner outputs, rich, lean, etc.? Is there a YT video that addresses these questions? Bottomline: How does the ECM/PCM adjust for these two different fuel types with different optimum air/fuel ratios, or does it not, and what are the impacts on scanner readings and diagnosis? Again, is there a YT video that addresses these questions?

[@benhawke7231]

I wish I could call you. I have an issue where I have negative short-term trim but the long-term trim never changes and the engine bugs at high RPM and Lacks enough power that it won't shift out of first gear.

[@kcuhc84]

I have a question. The car is running rich, the ECU is reducing the injector pulse time to compensate, the fuel trims are negative. The car is no longer running rich. Does this still contaminate the oil?

[@FranksWorld1]

Exactly my thoughts…. Sounds like nothing needs to be done… ecu has already corrected fuel delivery rate… all should be good now… right.???

[@tilemarblegranite]

Amazing!

[@76089randy]

My fuel trim atm on bank 2 is -25 on the short term

[@Xxxxxrrr6464]

Thanks

[@louisvillalba7695]

I love Jesus

[@Poocang_golfr]

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

[@AVIONDEMAND]

I would have to say, you need to check the fuel trims, look for any exhaust leaks, and then check the response of the upstream oxygen sensor. If you find any leaks repeat the process over and over. Graphing the oxygen sensor outputs with a scan tool is a great help too. For more advice talk to a local auto shop or visit our website aviondemand.com. Have a great day! -J. from AVI

[@Tootoojackson]

have short term bank 1 reading 25.0 and Short term bank 2 reading is 25.0 then both goes back down to 0.0 then go back up to 25.0 I was looking at the fuel system 1 and fuel system 2 it's saying open loop fault when I step on the gas to 2500RPM and let it go the short term drop down to 0.0 I have a vacuum leak somewhere

[@mustyali9529]

2006 Acura TSX auto, having my LTFT between minus 5% and minus 8% consistently at both idle or at normal diving. No driveability issues, no check engine light. Starts right up first thing in the morning and even after it's fully warmed up. STFT is mostly between plus and minus 3% at idle or normal driving. Mileage is about 240k, what could be the issue?

[@danm1026]

That's normal. 10% is where you need to start looking.

[@SaVarMatner]

If it's a boosted vehicle you want to stay on the rich side to protect from knock and other lean issues. Plus the PCM is telling the ECU to cut back on fuel because it is rich which in turn can lead to better fuel mileage. I have a boosted 5.0 and mines stay around -3 to -2 STFT and -5 to -7 LTFT but go close to 0 during boost then they both add fuel after boost to compensate for the extra air that came during boost but drop back to those negative percentage mention above afterwards.

[@vwb7diyr189]

Same for turbo car?

[@Bart12349]

The longer it runs rich fuel; it will contaminate oil. Got it.

[@sutaywinpangsap674]

Agreed, I tried to clamp vacuum line from the engine and downstream O2 reports lean.

[@ankurpatil8628]

@AVI ON DEMAND Thank for video. Could you help me make sense of these STFT and LTFT values. I have 07 ford taurus, for bank 1 STFT stays between +/-3%, but LTFT stays constant at about -12% at Idle. Bank 2 is lean at idle with +12% total fuel trim. When I increase RPM to 2500, STFT jumps between +/-6% and LTFT stays constant at -19%. Bank 2 improves at 2500 RPM with about +6% total fuel trim. OBD says cylinder 1,2, and 6 misfire. I have tested injectors, replaced the leaking injector already. What do these trim value mean? How come bank 1 is rich and bank 2 is lean? Thank you.

[@keereshsathron7262]

I had the same issue, Change air filter and sparkplugs

[@alvinlawanto]

What makes fuel pressure go high?

[@MarzNet256]

A bad fuel pressure regulator.

[@abdoalzady6784]

What about postive value

[@keereshsathron7262]

vaccum leak

[@nadeem5476]

my car Reports negative ten long term fuel trim ONLY AT IDLE as I push gas pedal little bit like 1200 rpm or 1500 rpm the long term fuel trim comes to negative 3 or less immediately ! any one can tell me why it shows negative ten at idle only?

[@shinola228]

Did you clean the MAF sensor?

[@nadeem5476]

@@shinola228 my car has MAP SENSOR and I cleaned it and on scanner it's showing normal 30 kpa reading at idle.

[@RBPD92]

​@@nadeem5476did you find the solution mate?

[@nadeem5476]

@@RBPD92 no

[@Icandothatalsow]

Honda? Valve adjustment.

[@qa7103]

right on the money, and a mustache to go with..