XCTrackGuy

Sorry for the long post...

I have a 1993 4spd auto Corvette coupe (only 16k miles) that's been misbehaving since August 2010. Back in August it developed a stalling problem that seemed to occur at high engine temperature. It would stall, sometimes run a bit rough beforehand, but it was like someone turned the key and shut the car off usually. It wouldn't start easily afterwards, and if it did, it would die fast, until it cooled down. RPM didn't seem to matter while driving, it would just die. Occasionally I'd get a DTC36 (optispark high res code), but usually no error codes. In March or April I replaced the ICM and ignition coil and that seemed to fix the problem: no more consistent high temperature stall.

However, a few weeks ago I discovered there is still a problem. The 'vette would intermittently run rough at idle, like it was trying to stall, and when you would accelerate with anything more than a slight throttle opening, the car had trouble revving, would pop and sputter, etc. I also got a DTC36 again; so I replaced the optispark this past weekend with a dynaspark unit.

The dynaspark didn't fix the problem. It still idles roughly when it gets hot (200+ degrees), seems particularly lopey, etc...
The car also sounds like it is intermittently misfiring. If you rev it gently, it revs fine, but if you step on it, the revs drop and the car tries to die (the more throttle you apply, the more aggressively it falls flat). However, if you rev it gently to say, 2000rpms, and step on the gas, it runs fine. No error codes, except for an intermittent DTC22 (low voltage to the throttle position sensor). Naturally, if you unplug the TPS the car still hesitates under throttle as previously described.

While running the motor at night, I noticed that if you rev the engine, the spark plug wires occasionally emit blue flashes around the plug boots. I'm not sure if this is arcing or not, but I decided to replace the plug wires. I replaced the passenger side today (didn't seem to fix anything; both sides still emit some blue flashes as you rev it, more prominent when the motor is hot/and/or trying to stall) and I'm doing the drivers side as soon as I can get an extra set of hands to help me out (maybe this weekend)...

Any thoughts on what may be causing this problem?

Repzard

jaa1992

OK, you bought a recent Dynaspark - do a search and you will find folks are less than pleased with them these days.
I bought one for my 92 back 5 years ago - it is fine

I'm guessing one of three things:
Connection with the ICM
Connection between the opti harness and the ECM harness (Passenger side of the intake, you did some work here to install the Dynaspark)
Dynaspark is bad

When I put the 383 in my car I couldn't get a real cheap opti from Chandler Motorsports at the time to try so I wound up with a Summit Racing white box. It has been fine until the 383 decided to eat a lifter, timing chain, etc.

I'd give the Chandler opti a try since its about 1/3 the price of the Dynaspark.

XCTrackGuy

Yes, I've seen people dissatisfied with the quality. But I would assume, if it was the distributor (or a connector), the issue would occur all the time, NOT just when hot.

The problem isn't intermittent, and the hesitation issue is extremely minor or non-existent until the car has warmed up.

C409

Vacuum leak ? ... Spark plugs ? gap ? ... you shouldn't see any blue flashing ...

jaa1992

My 92 was the same way. If I could keep it under 210 water everything was fine. Took someones sage advice and worked on all connections to make sure they were electrically tight. Problem went away - YMMV

Find the post by the guy that took a recent Dynaspark apart - I'll never buy another and won't send the one I have in for repair.

Shock96

Maybe try tossing in a 180 thermostat?

dewfall

Great, just what I needed to find out now. I got a dynaspark just a few weeks ago thinking it was a high quality part. If the thing won't work up to expectation for the high price tag I want my money back.