Long term Fuel Trim whacked out, with GRAPH

If ltft is lean it could be compensating for a leaking (rich) injector

 

Leaking /open injector would force fuel trims negative.

Positive fuel trim would be from clogged or low output injector (if an injector problem, I think unlikely at this point)

 

Thomas,

Sorry for not weighing in sooner.......just to eliminate the vacuum leak possibility could you note the ST and LT readings at idle (warmed up, closed loop) then advance and hold RPMs to 2500 for two minutes. If you see ST drop immediately and LT starts falling that indicates a vacuum leak. I realize you just posted that LT does not change from idle to 4000 rpm but the nature of how it works means it takes a while for LT to actually drop and that it won't drop if the rpms are constantly changing.

At least this test will put you on the right path.

 

Frankly, I have never seen one Bank offsetting the other Bank like this. You have a reverse correlation between the banks based on the data. For the ECU to do that it is getting confused signalling. It seems like the O2 sensors are cross wired or connected wrong. Leaking injectors usually only impact one Bank independent of the other.

 

Need this along with long terms to see the whole picture.

 

Also, I would double check the O2 sensor (pre and post cat) to make sure that they didn't get swapped.

 

Have you checked the O-rings seals on the injectors?

 

Did you check fuel trims before the major service?

Did you check cam timing?

 

Without knowing trims before, I would wonder if part of this problem is a bank to bank variance with cam timing if it was never checked.

 

Okay this is helpful. Bank 1 is pegged positive for LTFT. Bank 2 is okay and I'm going to ignore what is going on with STFT on both Banks. I'm probably telling you what you already know (so bear with me as I walk through the logic with you)......it is running way too Running too lean – High positive fuel corrections can be traced to:
1) MAF
2) O2 sensor faults
3) vacuum leaks from intake gaskets/hoses
4) unmetered air (intake snorkel leak)
5) clogged or dirty fuel injectors
6) fuel delivery issues
7) exhaust restrictions such as a clogged catalytic converter.

I believe you have chased most of these items already so let's presume that the O2 sensors are correct. It could be a coincidence or it could be related to something that happened during the major. If the O2 sensors are correct then the problem is on Bank 1. The problem is affecting all four injectors or only one of them. Of the remaining possibilities that leaves us with:

5) clogged or dirty fuel injectors
6) fuel delivery issues on Bank 1
7) exhaust restrictions such as a clogged catalytic converter.

So....based on what you have done so far....what appears left is:

1) a bad fuel pressure regulator ....affecting all four cylinders
2) a bad injector affecting one cylinder
3) a bad catalytic converter affecting all four cylinders

None of that is easy to diagnose. You could swap Regulator Bank positions to see if the problem moves. I would first check the vacuum line to the Regulator and make sure it is okay.

 

I tried to edit the above post but ran out of time. INTMD8 is also correct....it could be a mistimed cam although I sincerely hope that is not the case.

 

The answer is yes.....if Bank 1 throttle body is open at idle that could also cause Bank 1 to be getting way too much air. It could also possibly explain the inverse STFT readings. Both sides should have the same range of motion.

 

Not sure what would be stopping throttle opening but doesnt seem right.

For comparison