rebuilt ls1 heads and cam running issues

[redmaroz]

First off thanks to every ones post on here that have helped me out over the last couple years. I just got my ls1 engine assembled and in the car, its a 92 z28 if that matters any. But the engine is fresh, prc stage 2.5 5.3 heads with howards asa cam and comp 1.8 rockers. cam specs are 226/236 and .525 lift before the 1.8 rockers. I had this set up before the rebuild but i had a timing chain pin walk out and wiped out my engine. Before the chain went i had the car running and driving, it was short lived but it did drive. So fast forward to yesterday and i go to start it and its backfiring, not holding an idle unless i staid on it. i have double and tripled checked for vacume leaks, checked plugs, went over different parts of my tune and can not figure out what is going on. It will not idle unless i stay on the throttle and if i let off it dies and backfires some. I have attached my tune. i also checked for codes being thrown and there hasnt been any. The cam was installed and degreed correctly so i know thats not it. im at my wits end because im not sure what it is.

[dermotw]

If that is an SD only setup then the DTCs for the MAF aren't set right, should be fail on 1st error. Or, if the MAF's supposed to be on, then the ECT vs. IAT is wrong, and the MAF frequency fail high is at 0. Also, seems to me that the idle parameters are more changed than I'd expect?

Edit: got decent fuel pressure?

[5FDP]

Yup what he said. Being that the OS is upgraded to a speed density enhanced OS, you need to set the MAF dtc's to fail on first error.

[redmaroz]

Ill change the error codes, and yes fuel pressure is good. Any suggestions for idle settings? Thanks guys

[jakezed22]

Under Adaptive idle air flow you have the cells for P/N entered as 0 ?? I compared to mine and i have 4.0, -23.8, 0.0100 for the three P/N cells

[redmaroz]

Ive never messed with that one, its a 6 speed so im not sure if that's why p/n is 0 out?

[jakezed22]

Ah ok im auto so thats probably the difference

[redmaroz]

Thanks though, I appreciate it.

[mbray01]

if it ran with the tune before, and everything mechanically is the same except for being rebuilt, The tune is not going to be your problem. It is going to be mechanical. If I were to guess, I would say possibly the pushrods are too long now. If the heads were decked, and block too coupled with the 1.8 rockers. I'm sure you can see where I'm going with this. I would double check lifter preload

[redmaroz]

I double checked all of that and actually went with a shorter pushrod then before, I think I may have found the culprit in my wiring. Thanks, I do appreciate the help.

[redmaroz]

It runs! Thanks guys! It was the passenger side coil harness.

[redmaroz]

ok so im trying to get this thing drivable and its being a pain. when im taking off from park its showing me in the red up to about 2k like stft's up to 45. ive also attached where i am at with my tune so far. I am still trying to get the tps volts at 55 or less and get my iac counts down to, which go along pretty well until what you see with my stft. any help is appreciated so i can get this thing somewhat driveable. thanks everyone fyi its the 1st attachment

[IARLLC]

It is quite possible that with your fuel trims so far off you won't be able to get what you want from the idle until you work out the fueling. If I were you at this point I would make as much as a 20-25% change in the lower regions of the VE table where your fuel trims are so far off. This may seriously improve your idle and drivability so that you can move ahead with a normal tuning program.

[redmaroz]

Thanks man that and pulling some timing got it driveable. I appreciate the help.

[redmaroz]

another question for you guys, when i set up my wideband and the afr error histogram the little bit of logging i did today was showing -12.5 and -12.6 across the range i covered...is that right? i attached a scan of what im talking about. i went over all the how to's just not sure its right, Thanks.

[redmaroz]

never mind, I think I got it figured out.

[redmaroz]

Ok so I guess I do have 1 more thing im not clear on, as far as the afr error histogram goes. under graphs should I have selected afr error, or eq error for the histogram, its not very clear on the how to. the afr error is working, but I don't know if that's the right one to be using to make the corrections to my ve table. I am wanting to tune by afr at this time not lambda if that helps any. Any help is appreciated, thanks.

[5FDP]

Use AFR error if you are tuning with regular AFR and not Lambda. You'd use eq error if you were tuning in lambda.

[redmaroz]

Ok, thanks for clearing that up for me.

[redmaroz]

Ok, so the car is running a little better each day. I actually drove it to work yesterday which is about 60 miles round trip and it did really well overall except for 1 instance. I was about 5 miles from home on my way back from work and the car was completely warmed up and as I was coming to a stop the idle dropped and it started acing like it was going to sputter out and die. It didn't, but it only did it that one time and everything else was good to and from. I will post up the log and tune when I get home later today but just wanted some suggestions what to look at in the tune that would cause that. I have the idle still set high at 1000 right now till I am able to get everything set, and I know im still running a little rich. My iac counts at around 185-190 were 30. From what I have read I thought that was in the acceptable range of counts for a cammed car. Thanks again everyone.