Setup a histogram to monitor LTFT vs MAF frequency. Look for any abnormally high positive or negative values (the positive ones in excess of 20 will set p0171, the negative ones will set p0172). Adjust your MAF calibration in those cells by that same percentage. If you are receiving misfires after doing this, it might be bad fuel injector settings.

 

Agreed. thats what i was trying to say when i told him to tune his MAF. You explained it better though.

I would think that the stage 2 tune would have ruled out any major fueling errors with the 42s leaving the maf as the culprit, but never know. stranger things have happened...

 

Ya, I'm not experiencing any misfire problems with the 42s so I'm taking it that the fuel settings were not right with the 60s. Is there a how to on speicifically how to tune the MAF settings using the fuel trims??

 

Is/was your idle rough, or have alot of fluctuation?

the only how to i found was https://www.cobaltss.net/forums/how-guide-43/how-tune-60lb-injectors-56k-%3D-zzzzzzz-111378/ but it deals more with wideband tuning than fuel trim tuning. same principle though. you have to set up a histogram to plot your fuel trim error VS MAF frequency. fuel trim error is LTFT + STFT. IIRC the formula is [SENS]114.IMP + [SENS]116.IMP or somethin to that effect. you have to look for it in the sensor list when you make your custom PID.

 

alright. it sounds very complicated but I was told it wasn't too bad...also when monitoring the fuel trims. do I need to stay out of pe mode? ii read something like that.

 

Try to stay out of PE. Your MAF cal is probably off everywhere and should be fixed while in PE with a wideband. You can do it with a plot filter and adjust both at the same time but that can get a bit involved if youve never done it before.

In case you want to know, setup two histograms, one for LTFT vs maf freq, and one with your wideband to monitor AFR error. Set a plot filter on the wideband histo to only monitor values when commanded afr is less than 14:1. I dont have the specific settings on me but if youve ever setup a plot filter youll know what Im talking about, if not just ignore this.

 

...

This means unmetered air is getting into your engine (post-MAF). I had this problem, turns out my intake tubing came loose where it bends to go into the fender well. Re-connect, and all was well. Check and make sure your intake is hooked up properly, clean your MAF and SCIP sensors with sensor cleaner. Try again.

 

UPDATE: Put the 60s back in. We didn't have time to tune the MAF but I did still throw a lean code, but no misfires. So hopefully we can solve the problem when we tune the MAF. Unfortuantely, me and my tuner are pretty much new to this. The basic stuff is no problem, but tuning the MAF seems a little more involved. I will read up on it more and hopefully understand how to do it. If anyone has any specific pointers it would be greatly appreciated.

 

UPDATE:Ruled out the MAF calibration. It was tuned accurately by Fast98. Tried different tunes and same result. I'm throwing the P0171 at idle along with misfire in cylinder 1. I hooked up my interceptor and had 16 misfires in a matter of a couple of min in cylinder 1.

 

fixed

 

short pulsewidth errors. maybe a messed up spark plug. idk wtf else it could be

 

I'm gonna throw in some new plugs tomorrow to see...would a vacuum leak cause it to misfire??

 

not likely, but it would cause your lean code.

 

A bad coil pack (which would actually start to become much more severe while under boost) or something else electronically can cause the lean code as it would skew air/fuel ratio and o2 output voltage causing fuel trims to spike. You should notice a steady misfire under load in most cases if its severe enough to affect afr.

 

After driving it this morning w/ the interceptor...no misfires under load, but it will have a couple every stoplight, most in cylinder 1 but a few in cylinder 2. None in 3 or 4 yet..But its not throwing the misfire code as of now. Would it be possible to have something damaged like fuel rail or injector seats?

 

my car is doing the same thing but idk it run like a b*#@

 

Is it really doing it? Mine still runs good under load as well, but at idle is another story.

 

It is possible that you tore the 0-rings on the plastic seats or the injectors themselves, or they just are crooked and not sealing right causing your vac leak.

I was going to say coil pack as well but i hesitated since you dont have problems under load.

i'd also pull the plugs just to see if they are fouled, toasted, or improperly gapped...

 

Bump for some more info. Replaced the spark plugs and no improvement.

 

unplug your number 1 and 3 coil packs and switch them (leaving the wires in original position) If your misfires move from 1 to 3 then its the coil. I actually have a spare coil pack laying around if that is teh problem... but i dont really think it is.

 

all you need to fix your car is .25cent of gasoline and a box of matches kaboom

 

Another update: I'm throwing a P2261 code now along with P0171 and P0300. P2261 is the Bypas Valve Mechanical code. Any ideas? Hoses are hooked up? Leak? How do I check it?

 

lol check the hoses for cracks. then take the vacuum lines off the bypass solenoid (the solenoid, not the actuator), seal them off, and see if it still misfires and throws codes.

 

Just as an aside, my car also throws a ton of misfires in cyl 1 at idle according to the interceptor. I think it's just the interceptor reading wrong or engine detecting misfires incorrectly.

 

ok ive thrown this code before when i hooked up my tech 2 in shop.... we also have the whole ob2 online thing for gm and crap but anyways it told me all the reasons why it could be throwing this code i dont remember some of them but my problem was because i put some lucas fuel additve in my gas and caused it and i quote ( to much alchol)