Does anyone happen to know what the normal operating fuel trims should be at. I have a scanner and the ability to view them, but don't know where they should be. I believe i have a vacuum leak but before i search for it i want to know if i am looking for the right thing.
I initially thought sensors also. However, i have checked and replaced all according sensors with no resolution. The only sensors that could be the issue are the O2 which i realize would be likely, but i have unplugged them one at a time and the truck ran no different. It is my understanding that the truck would go rich without the O2 input, and might not run well.....but would run. The head was replaced about a month ago and i believe that during the reassembly something wasn't snugged up correctly, hence my vacuum leak. If i knew where my fuel trims should be i should be able to verify my assumptions. Also fuel pressure is at 60 lbs, and injectors were checked when the head was off.
I appreciate any input from you guys.
Thanks
Also, is the PCM flash a dealer ordeal, and do you happen to know the parameters for the TSB for it. I just forked out $1100 for the new head because GM refused to cover it under the TSB for the valve seats. I was less than 2 months outside the 7 year coverage for the TSB, and only at 78,000 miles, but they refused to cover it (after escalating my claim 3 times.) I'm just a bit leery of anything Dealer related right now.
Thanks
Well i think i will give that a try, at least it's a place to start. The only dealer i still trust is about an hour away so i might not get to it till the weekend, but i guess that will give me more time to chase my tail. I appreciate the replies from all as i would like this to get this figured out as soon as possible, but also would still like to know those fuel trims if anyone has any info.
Thanks in advance
I know the coupler between the throttle body and resonator, the pcv hose, as well as the brake booster hose are all good as they were the first things i checked. There is one ground on the passenger side behind the air box that is corroded. I highly doubt it is the problem, but i might as well get the wire wheel out and make it shiny to rule it out. I'll post back.
Those connections were checked and re-checked, and then i applied di-electric grease so i know they are good. Also i don't have any misfire codes, just the lean code.
Ok i figured since i wasn't hearing any more idea i would put in some new info:
Engine Cold:
-Short term fuel trim: -2.3 to 2.3
Long term fuel trim: 6.2
Map: 32
Rpm: 790 to 810 (that is where it has always been)
Timing Advance: 9.5 to 13.5
Air Flow Rate: 4.96 to 5.21
Absolute Throttle Position: 18.4
O2 sensor 1: .08 to .80
O2 sensor 2: .725 to .735
Numbers at operating temp before it dies:
Short term fuel trim: -1.5 to 2.3
Long term fuel trim: 3.9
Map: 31-33 (dies at 27)
Rpm: 800
Timing advance: 6.0 to 10.5
Air flow rate: 4.38
Absolute throttle position: 17.6
O2 sensor 1: .745 to .110
O2 sensor 2: .786 to 2.33
What i have done: checked for vacuum leaks, checked MAF sensor, replaced cam and crank position sensors, crank relearn, replaced cam actuator solenoid, checked coils ( no miss and no codes)
The truck will not even throw a code now, it will just die....but only at operating temp, but then will fire right back up. It has a stored lean code, but will not throw it on the dash.
The last thing i can deduce is i have a bad O2, or a bad cat, but i don't want to throw money at it until i can be sure. If anyone has any input i would appreciate it, or other ideas. Thanks in advance.
Well fuel pressures have been checked twice and they have been steady and appropriate both times. I had the pcm wires off when i did the head so i guess that's a place to look. Getting tired of fighting this thing ha.
Checked all connections and grounds today, including the pcm harness to pcm. All connections are good and snug. All grounds are checked and wire wheeled clean then covered in di-grease. Truck ran ok at idle today for about 10 minutes at opreating temp, died once, started back up, ran for another 10. I goosed the throttle to about 4000 and let it drop. The rpm dropped to about 550 before it caught itself, came back up to 800, then died. Started back up, ran for 5 mins fine, goosed it again, same deal dropped to 550 before it caught itself, jumped to 800 then died. I will need to put a fuel pressure gauge on it during this to see if it drops off or something because it seems likely that is the cause. However, i have 60 pounds at idle which is right where it should be, and it seems odd that it would, but who knows. I'm running out of ideas and starting to hate this truck. It's almost walleye season and my boat doesn't pull itself!
Not so far, it's on my to do list. Money is tight right now. I'm a college student and the 1100-1200 for the new head just about broke me. Paycheck by paycheck ha.
Yes this has been the same theme since the new head. I did all the work myself, and admit i'm not a perfect mechanic, but if there was something i didn't know i followed the manual to a T. I realize that the problems coinciding with the the new head are likely not a coincidence, i'm just trying to work backwards to find the problem. I've already got way more time than i ever thought i would vested into the head debakle, and am just trying to get it fixed to protect my sanity. I will give the dealer a call tomorrow to see what they quote me for the pcm update, i just know you are hard pressed to find a dealer by me that will work on anything for less than an hours labor (95-115$.) I guess i will see what they say.
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