My IROC is driving me insane. It's a 350 5 speed. I've been having problems starting the car since I swapped to a 165 ECM. When it first fires, if I catch the throttle just right, then hold it at 2k rpm, it'll stay running. After a minute or two, I can take my foot off the gas and it'll idle well. If I don't get lucky on the first try, the car will just fire and die immediately.

I don't get any codes. I've reset my minimum idle a million times, changed the IAC, and testing the IAC wiring. I'm running a slightly modified APYP bin (corvette 6 speed bin). I'm going to check my fuel pressure tonight, but since the car runs rich (when it runs), I don't think fuel pressure is a problem. Timing is conservative, at around 6*.

I don't have a cold start injector, but since the APYP bin is designed for a car without it, that shouldn't be a problem either. My coolant temp sensor is functioning properly.

When the car does actually run, the rpms drop VERY quickly between shifts. I think this may be related to my starting problem, although I'm not certain. I've checked my vacuum lines a hundred times, and even after the car is shut off for a while, if I pull the line off the vacuum reservoir cannister, I can hear it sucking air. It doesn't appear that I have a vacuum leak, although I haven't had a gauge on it yet.

Any ideas? I've been beating my head over this since last fall and haven't found a single damn thing.

Oh yeah... it only does this when the car is cold. It starts fine when it's warmed up.

 

Jim,

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Cracking the throttle is doing a few things..

Changing TPS voltage. (maybe set TPS higher?)
Allowing more air into engine. (see IAC counts, Turn the key on, monitor IAC counts, make sure it's opening)
Allowing more air through MAF. (unplug MAF electrical connector on cold start)

More than likely though, since this began when you changed to the 165ECM and new PROM setting, it's a matter of programming the PROM setting for cold start with your engine combination. IIRC you're running more engine than the stock Vette's? Have you tried for help on the DIY PROM Board?

 

I'm not sure if I have "more" engine or not. I have 461 fuelie heads, which I believe are supposed to flow more than the 113 aluminum vette heads, but some disagree. In any case, other than having iron vs. aluminum heads, my motor should be simililar. I think it should at least be similar enough to start when I turn the key! Even the stock 305 chip with the old 870 ECM didn't have startup trouble like this.

I had an ARAP chip in there at first, and I had the same type of startup problems. I hoped that converting to a bin designed for a manual transmission might help, but no dice. I might try a stock LB9 5 speed bin with a bigger injector constant just to see what happens, but my gut tells me that this is not chip related.

 

I threw a fuel pressure gauge on it last night. The pressure bleeds off a little faster than I'd like to see, but nothing that should prevent me from starting the car. Tonight or tomorrow I'm going to try swapping the coil from my GTA and see if it makes a difference.

The damn car is starting to kill the grass on the lawn.