Recently purchased a '91 Camaro Z28 from an older fellow who garage stored it for ten years and took it for the occasional drive. Some modifications put in during this time have been: the smog pump was removed and the AC was left in, but the serpentine belt was rerouted from the tensioner directly to the crank. Exhaust headers were added. The cooling fans were rewired to turn on immediately and simultaneously. A Hypertech performance chip dated 1996 was found in the ECM; a Thermomaster (previous owner ordered) is on the way. (I would like to DIY PROM, but I haven't advanced as far yet.)

The spark plugs are new and firing, the fuel pump is priming, the battery gives 12+V; although the battery connects needed a cleaning, the alternator appears fairly new, the fuses and relays have been checked (to the best of my knowledge where the @#$% they are), and the fuel filter is going to be changed tomorrow. It started without a problem 3 days ago and then stalled a bit before starting yesterday but made it through the city without stalling. The older fellow said it was the first time it hadn't stalled and he's been having trouble getting it to start for awhile. Last night and today, she's angry at us and won't start at all but the engine turns, the EST functions and the fuel pump primes. He seemed convinced it was the performance chip in the ECM that was the problem and it would die out soon and I'm starting to believe him. I'm just wondering if anyone has experienced similar problems related to the chips? Or ICM?

 

Do you have any codes? Next thing to do is ohm your injectors. You are testing for ohms with each injector.

 

Air delete should not be issue.'thermomaster chip us a waste of money.

Check for trouble codes as mentioned.

 

No trouble codes with the paperclip test; the usual code 12 flash.

I'll check the injectors today and get back to you on those. I'm assuming ~16 ohm is normal?

Also, the ICM has been mentioned with this car frequently and it's a cheap part, but I'm a little concerned on how to remove the distributor without affecting alignment. I believe it's one with an internal capacitor; any info is great.

 

could be clogged injectors or bad o2 sensors

 

I have had two camaro's that had running trouble and both were the distributor i put in the MSD Pro-Billet part#8366 now it purrs like a kitten also but unrelated i chose to get my chip from Harris performance sweet custom burn chip also when i upgraded to a 838 he cut me a new chip and i could not be happier

 

I feel like I just wasted ten minutes reading details that had nothing to do with the car...

 

no big deal, you can mark the distributor housing. There is really no set ohms on the injectors, just make sure they all come out to about the same.

 

I love pictures

 

Probably not the cause of the stalling, but I'd go back to the stock chip if you have or can get one. Generic aftermarket chips are of no real value. The most they can accomplish is pull some tricks to make it feel more powerful at partial throttle, but at WOT they don't actually improve anything. What they're best at is hurting fuel mileage.
GM tuned their chips to make power at heavy throttle and to get mileage otherwise. That's probably what you want.
Doing a DIY chip is fine, because you'd be starting from the factory tune and customizing it based on the behavior of your car, and your own preferences.

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Does it have old gas in it?

Check the fuel pressure. Not sure what the spec is. With the engine running, it should also fluctuate in response to manifold pressure, maintaining a consistent pressure differential. With the key turned back off, it should hold pressure for a long time, as in no more than a few psi lost in 20-30 minutes, the less the better.
I don't think the latter point relates to your symptoms, but as long as you're checking might as well watch for it.

It could be useful to get/make an ALDL cable and hook the car up to a laptop with a utility like WinALDL. Then you can watch the sensor readings as the car is running. This might reveal sensor related problems. Many times there are issues that don't trigger a "check engine" light, because the ECM isn't smart enough to realize the readings are bad, or they're too sporadic to get flagged.