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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > LTFT High!



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      02-07-2018, 08:54 PM   #1
bmw335ichoppa
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LTFT High!

Hi Guys,

i have a 2010 e90 335i with 94kms on the clock,

i have been trying to work out why my LTFT's on both banks are high. This is what i have checked.

O2 sensors all good
Vac lines all good
RCV replaced all good.

My LTFT's do go down on WOT but i done a smoke test and I've got no leaks.

The only thing i haven't replaced is the PCV valve which i have ordered.

Everything seems to be running great, even on idle.

can you guys suggest anything else it could be?
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      02-07-2018, 11:07 PM   #2
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Wow another guy that has a LTFT issue. Im in the same boat. Do you have downpipes installed? Do you have a multi gear log?

Last edited by tan_rich; 02-07-2018 at 11:17 PM..
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      02-08-2018, 07:45 AM   #3
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My car is completly stock. No mods. My figures show as

Ltft bank 1: +17 at 700rpm
Ltft bank 2: +26 at 700rpm

Ltft bank 1: +5 at 2000rpm
Ltft bank 2: +10 at 2000rpm


I can only put it down to the pcv valve, check hose, tmap or some vacuum leak i havent picked up
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      02-08-2018, 08:03 AM   #4
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How do you know the O2 sensors are "all good?" What metric are you using to test them?

What do your STFT look like?

Post a log if you want any help outside of conjecture.
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      02-08-2018, 06:21 PM   #5
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Well that would be the last thing as i find it very unlikely for both sensors to go at the same time. Plus, they are both well within translation with each other and voltage fluctuation seems ok.

I only have a simple OBD2 app that cannot export. I'm getting the cable now so i can run INPA.

STFT: +-3 on bank 1 - Idle
STFT: +-4 on bank 2 - Idle

STFT: +15 on bank 1 - 2500RPM
STFT: +22 on bank 2 - 2500RPM

On load, STFT will go up and LTFT will come down.
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      02-10-2018, 10:37 PM   #6
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New injectors fixed my trim issues. I had index 9s and replaced with index 12s.
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      02-12-2018, 10:15 AM   #7
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Quote:
Originally Posted by kfrazie1 View Post
New injectors fixed my trim issues. I had index 9s and replaced with index 12s.
Hmm...I could see leaky injectors causing negative trim values, but OP seems to have the opposite problem.
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      02-12-2018, 05:00 PM   #8
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as o2s age they just react slower, log term trims in and of themselves (high or low) dont mean a prob as such. Do you have some driveability issue? By inference, a long term trim adding fuel consistently in the same rpm would band would be associated with excessively lean and cause a surge.

You experiencing that?
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      02-12-2018, 05:49 PM   #9
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Quote:
Originally Posted by bmw335ichoppa View Post
Well that would be the last thing as i find it very unlikely for both sensors to go at the same time. Plus, they are both well within translation with each other and voltage fluctuation seems ok.

I only have a simple OBD2 app that cannot export. I'm getting the cable now so i can run INPA.

STFT: +-3 on bank 1 - Idle
STFT: +-4 on bank 2 - Idle

STFT: +15 on bank 1 - 2500RPM
STFT: +22 on bank 2 - 2500RPM

On load, STFT will go up and LTFT will come down.
I had same problem on both both like you. Mine was defective DME although you wouldn't think it was...10K in parts and 2 year later I fixed it. Injector first then DME. This is not an air leak. Post a log as it will help. If you LTFT are very transient and look more like a O2 sensor log then it most likely the DME
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      02-12-2018, 10:51 PM   #10
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Quote:
Originally Posted by FCobra94 View Post
Hmm...I could see leaky injectors causing negative trim values, but OP seems to have the opposite problem.
Actually, my issue was I was maxxing my STFT at +33 during WOT on 93 octane. Struggled with this issue for 2 years and finally just changed all injectors and it solved my particular issue. YMMV
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      02-12-2018, 10:53 PM   #11
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Also, clean your TMAP sensor - may help.
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