Fuel trim problems

[imblaze89]

How's this one any better?? Says system lean tho. Took everything apart and pressure test the front mount with a tire stem and smoke test the vacuum lines.. ther was def a leak in the front mount but its not even hooked up rite now didnt see any in vacuum leaks..numbers are up quite a bit after putting all back together.. If this doesn't fly gues il try the sensors. Thanx evey1 for the quik replys can some1 tell me how to start a new thread?

[iNVAR]

what the hell, your trims are all over the place. now it looks more like a post-turbo intake leak with it dumping fuel into trim B. but if it were, trim A would be positive also.

 

p.s. i hope you're staying out of boost. but it doesn't look like you are. stay out of boost.

[imblaze89]

Ok im gonna try replacing a few sensors so by the front o2 u mean the one under car near manifold not the one in the up pipe correct?

[BarManBean]

Ok im gonna try replacing a few sensors so by the front o2 u mean the one under car near manifold not the one in the up pipe correct?

 

Correct. O2 sensor is in the manifold--the sensor in the up pipe is an EGT sensor.

[imblaze89]

Someone plz tell me how to start a new thread

[Zander916]

The ECU believes, correctly or not, that the AFR in closed loop is richer than it has targeted. To correct this it is reducing injector pulse width via the four fuel trims A thru D. If you had an air leak you'd expect the reverse happening.

 

As it is the system is trending almost to limit where you'll throw a code for system too lean. Remember it takes a little time for the trims to settle to a final value and it only gets adjusted while operating in that load range.

 

The few times I've seen this the following problems were found:

 

1. Failing MAF sensor giving a high reading, misleading the ECU to believe more air is flowing than is the case, leading to rich condition.

 

2. Faulty O2 sensor reads richer than real AFR.

 

3. Dirty or failing fuel injector(s) which stick slightly open and don't control fuel flow properly.

 

The fact that you have a trouble code for rear O2 too lean makes me question the front O2 sensor, which provides feedback for fueling that the trims derive from. The front O2 is saying the fueling is too rich across the board and the trims are a result of that. Somehow, the rear O2 disagrees.

Note that the trim value in range D is applied to open loop fueling. Normally a rich mixture helps control knock. The fact that you have IAM at <1 leads me to think you are actually running lean in open loop and knocking, which causes IAM to drop.

 

I would swap the front O2 sensor with a known good part as a first step.

 

 

I agree with this. My O2 is bad right now, no codes, running rich as hell. I've lost track of who has what problem.

 

But to the person running lean. (14+ stft). IF in fact you've eliminated all leaks then I personally would suspect possibly an injector. The O2 is reading from all cylinders so if one is running lean, it will show up there but the way to get an idea of which one MIGHT be bad. See if you can determine which one the misfire is on. If it's all #4 for example. Swap it with another and see if the misfire follows. If you suspect the O2 you can do what I did. I unhooked it. After that mine ran great. (Just stay out of boost until it's replaced)

It still could be a MAF too but I'm doubtful on that one.

 

To the person running rich. Mine has been running rich and is without question the O2. You can unhook it and see if it is better. (Sets a code naturally but no biggie) Are you having misfires?

If you are, a coil or spark plug could be toast and the unburnt fuel is read by the O2, indicating rich mixture.

Or as was said, an injector sticking open.

How is the gas mileage? I was getting 11mpg just old man driving it.

 

I'd watch the STFT for immediate readings. The LTFT's will take a while to settle, as was said in the quote above. Just be mindful that for example when you first hit the throttle it will go rich but just for a second and when you let off it can go rich or lean for a second. Don't mind that. I discovered my STFT's off just sitting at idle. (-8 to -11)

 

 

I hope this has been helpful.

[imblaze89]

Turns out my factory ic was cracked on the end.. Went bak to fmic fixed couple leaks on it and got this..how's it look?

[BarManBean]

[ATTACH]156399[/ATTACH]Turns out my factory ic was cracked on the end.. Went bak to fmic fixed couple leaks on it and got this..how's it look?

 

still looks horrible.

[fahr_side]

Ugh

[imblaze89]

What's it supposed to look like?

[BarManBean]

Like this. A whole lot of zeros is a good thing.

 

Your high-load fuel trim is just a touch low, but overall the trims seem ok. However, your car is throwing multiple codes and you have learned knock all over the place.

 

Edit: and as iNVAR says below, you IAM is also less than 1.00. Never a good thing.

[iNVAR]

And his IAM is below 1. Phoeey.

[ibr_adam09]

How bout this delimma ?

 

- -15.0 in the first three cells

- 0.0 in cell D

- no knock, all 0 values and IAM 1

- afr on target around 14.7 at idle

- new maf, afr sensor (front and rear), no air leaks.

 

This is the issues I've had after my last tune.

[BarManBean]

How bout this delimma ?

 

- -15.0 in the first three cells

- 0.0 in cell D

- no knock, all 0 values and IAM 1

- afr on target around 14.7 at idle

- new maf, afr sensor (front and rear), no air leaks.

 

This is the issues I've had after my last tune.

 

By no leak I assume that means you have done a boost leak test? I had an issue with my airbox--wasn't sealing correctly. The issue wouldn't show up with a boost leak test / smoke test.

 

If you have an aftermarket filter in there, swap it back to stock and close everything up really well again. Mine was only causing issues in the idle trim, but it's worth a shot...?

[ibr_adam09]

I have a cai, injectors, 18g, fmic, lots of stuff. and yes boost leak test, water/soap test and tested the inlet.

 

The injectors have less than a 15k.

 

I could only think that the aos or battery relocation has something to do with it. That desperate in finding out what it is.

[yardie]

To imblaze89, I had the same hard starting and weird trims as you do, i had my injectors cleaned, changed fpr and plugs to no result. What fixed it is hard to describe 'cause I did everything at once, I swapped injectors, fuel pump and installed the stock tgvs. It could well be a leaking tgv to manifold gasket/ o-ring messing with the trims and a stuck injector causing hard starts. Hope this helps.