vac leak/cat diagnostic?

[gpjohnny07]

Here is my situation:

I'm running an 05 pcm in an 07 GP n/a. Just installed headers yesterday. I've been trying to get this pcm running properly for about 2-3 months now, and i keep switching it back to stock (the 07 pcm cannot be tuned). I am running into the following issues with the 05...My fuel trims seem to be stuck at 16.4, but are not that way all the time. I am getting lots of KR (up to 8*) at medium throttle levels. I am wondering if someone can take a look at my scan. I have attached my scan and the tune that i have on the pcm. I also need some information on how to get out of VE tuning. I have heard that i should not be tuning with VE. I can't seem to figure out in the program how to change it. Am I having a vac leak? Is it just a cat diagnostic? Why am i getting less than 16mpg's on an n/a vehicle???

[Shane Hewitt]

Try these values in your Injector Flow Rate vs. Kpa Vac table & see how that works for you.

Looks like on avg. your LTFT + STFT are having to add approx. 31%. Coincidentally, your injector scale is about 31% higher than these stock values from an '04 Grand Prix file I have here on my laptop. Other than the injector discrepancy, the files I compared are very similar. So, unless you've changed injectors, give these stock values a go. I would suspect everything should fall right into place.

Labels -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100
Fuel Flow 16.21 16.21 16.21 16.21 16.21 16.21 16.43 16.65 16.84 17.04 17.16 17.28 17.57 17.82 17.98 18.15

[passingpower]

I've never witnessed this myself being an 01 but, I think your answer is in here:
http://www.hptuners.com/forum/showthread.php?t=18516

Sounds like the diagnostic.
If you want to confirm a vac leak, spray all the vac lines and intake gaskets with brake or carb/TB cleaner while at idle. When you hit a leak, the cleaner will disrupt the oxygen flow and cause a change in idle speed. Hit it again. can you repeat the stumble/surge? Congratulations, you just found your leak.

[gpjohnny07]

update: i got another member who runs an 05 pcm in his 07 gp to send me his tables, and they were different from mine. i flashed this tune to the PCM, and attached is the scan i did. IMO, it looks much better, but i still need some help...i also attached my DTCs...thanks

[Shane Hewitt]

What differences did you observe between the 2 files?

Just curious as to what the culprit was. It is definitely a big improvement over the first log you posted.

[gpjohnny07]

the fuel rates were actually off, the tune that the other guy sent me had the correct flow rates. i noticed that the ltft's were actually MOVING!!! Thats really all i noticed. i'm still new to this, so any insight is greatly appreciated. i am no longer thinking this is a vac leak. i think i might be getting some of that cat diagnostic test though...i really just need to know if this is safe to be driving on...hence, why i only ran a short scan on it...

[gpjohnny07]

now, since i changed the flow rate, do i need to relearn the fuel trims? i've heard that i should do this...

[Phantom]

I would clear all codes and reset the fuel trims in the scanner.

Do you have an air pump on the car?

[gpjohnny07]

i don't think i have an air pump. and i don't know how to clear the codes...how do you do that?

[gpjohnny07]

nm, i figured out how to clear the codes...i no longer have SES lights