A friend of mine recently swapped a 6.0 out of a 2003 denali into his 67 camaro, stock heads and intake, with a mild (220ish duration) cam. I had just barely started tuning it when he decided that he was going to just swap to a car intake instead of trying to find a cowl hood that would clear the truck intake so I stopped tuning until he finished the swap.
I had basically just done a little VE work around idle, upped the advance at idle a couple of degrees, and got it idling OK at 800 and we took it for a couple of spins around the block to make sure the trans was shifting ok and there weren't any leaks.
Fast forward a week or so and he was going to show off the car to another friend and he gets out of the shop and ~halfway down his driveway and the motor shuts off like he had turned off the key, and wouldn't even try to start. He figured out the fuel pump wasn't running, checked the fuse and the relay, both good. So he pulled the battery cable and reset the ECM, It would now start, but died just 30s-a minute later the same way, no fuel pump again. Reset it and this time it stayed running indefinitely. Over the next few days he figured out that it would only do this when cold, once you got it up to temp it was fine, also if you held it above idle, 1500 or so it would stay running fine but ran rough.
Well I was over there this afternoon just to shoot the shit, wasn't really planning on messing with the issue until we got the intake swap done but curiosity got the better of me. Sure enough 30-45s after we started it it dies like you shut the key off, no stumble no idle flair, nothing. Won't start, checked the wiring and it is definitely the computer not sending a fuel pump signal. We reset with the battery, does the same thing. Also noticed it was idling rougher than when I left off tuning, he said it gets better after it gets warmed up and figured it was just because I hadn't tuned it cold. Though it was noticeably better cold when I stopped a week or so ago.
So I went and grabbed the laptop and my tuner out of the car, I had to check and see if there were any codes, or if maybe I had missed something VATS related. All the VATS seems to be turned off, VATS type set to none, all three theft deterrence codes disabled fully. Scanner shows 3 codes, P0101 MAF which I expected since it is set to fail and 0HZ for the VE tuning, P0106 MAP sensor and P1514, the second two codes I hadn't seen before.
This is when he tells me about how it won't die if you rev it above idle, so I give it some throttle, about 1800-2000 rpm, but the RPMs are dropping 3-400 rpm every few seconds for a few seconds. unfortunately in my rush to check the codes I hadn't changed the scanned layout over from Rusk's base running airflow layout so there were a bunch of useful things I wasn't logging. But i did notice the cause of the rpm drop was the spark advance being gutted, or maybe that was a symptom, I just know it would go from the expected low to mid 30s down to 8-9 degrees whenever the RPM would drop.
Checked the codes again, and the p0106 and p1514 are back, reset the codes and the idle instantly gets better and the surge at part throttle is gone. By this time the engine is fairly warm, 150-160 degrees and it continues to run just fine for a good 20 minutes before we give up to try again when its cold.
Unfortunately I hadn't plugged the laptop into the wall, and it died before I could get the log saved, so I don't have anything to post, though I will post the tune that's currently on the ECM.
SO, with all that said, would either of those codes cause the ECm to shut the engine down and not let it start until they are cleared, or is the shutoff something unrelated. Also would those code cause the spark advance drop or is that unrelated/symptom of something else. I know I need to get a log going with knock retard and total retard, manifold pressure, is there anything else I should be logging that would be useful?
Looking into those codes it looks like a vacuum leak could be causing them both, but what would cause a vacuum leak only when the engine is cold? We checked for one after it had gotten warm and found nothing.
bobbies camaro ltft VE idle tuning.hpt
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