Long term fuel trim values

[LaCroixBoix]

Hi! I just got through removing my intake manifold to search for a missing DISA pin and replace the ccv while I'm at it, also did a new DISA, intake gasket, fuel injector o-rings and the idle has greatly improved though still rough enough to throw a CEL. I hooked up INPA and checked the LTFT with are at 1.1 and 1.55 which seems like a big discrepancy. Additionally the 227/228 codes being thrown are only showing 16.4% and 19.5% - I'm not sure how those should or do relate the the LTFT.

Any insights appreciated!

 

[LaCroixBoix]

Well I'm silly, just realized that the multiplicative value is on a scale from -50 -> +50 which puts me dead center! Just regular lean codes I suppose. More leaks to find.

 

[NZ00Z3]

Hi

I'm still learning about the INPA fuel trim information. Totally understand the OBD2 equivalent and how to use them for diagnostics.

Multipicative are very similar to the OBD2 long term fuel trims. Yours are looking very good being so near to 0%.

Intergrator are very similar to the OBD2 short term fuel trims. Being Lambda, 1 is the target. Your are showing 14% to 17% lean, that is the number minus 1.

The freeze frame data is saying the you have a high "Lambda Control Deviation" (lambdareglerabweichung) of 16% to 19% This is a very lean mixture at around 1,600 rpm

Quick vacuum leak test.
With a hot engine at idle, record the integrator and multipicative trims for both banks. If any are > 8% (integrator is number minus 1) then you likely have vacuum leaks.
Rev the engine to 3,000 rpm for 30 seconds.
Watch the integrator numbers. If they reduce significantly, might even go below 1 (rich mixture), then you have vacuum leaks to find.

Best way to find vacuum leaks is to smoke test the engine. See this thread: https://www.e46fanatics.com/threads/how-to-smoke-test.1261077/#post-18615547

 

[LaCroixBoix]

Great advice! Took it to the indy for some diagnostics and they found that the valve cover was warped - so that's up next.

 

[LaCroixBoix]

Great advice! Took it to the indy for some diagnostics and they found that the valve cover was warped - so that's up next.