’93 Z28 M6 – Car has developed the strangest misfire/stumble/hesitation/whatever you want to call it. I can’t seem to find any pattern to it. I can be driving along at any speed, any gear, any load, and any throttle position and the car will act as if I have turned the engine off for a split second. It isn’t just missing on 1 or 2 cylinders, the entire motor doesn’t fire. This lasts anywhere from a half to a full second then it will fire back up and run fine again. It lasts long enough that the tach has time to fall from whatever position it is in to zero, then comes back up when the motor refires. When it does refire, the SES light comes on and the fans stay on. I have the older style OnBoard Diagnostics (OBD1) and the only code it gives after this happens is code 36. If I stop, turn the car off, and restart it, the SES light stays off and the fans work normally until the next time it does this BS.

All of the other gauges and the radio work properly throughout the ordeal, so I don’t think it’s a battery cable or anything like that? The opti, plugs, and ICM have about 12k miles on them. The MSD cap, rotor, coil, and wires have 30K on them. I tried a new coil the other day and that didn’t help, so I took it back to the parts store and put the MSD coil back in. I tested the fuel pressure and it reads fine and constant throughout one these episodes. I am clueless….anyone have any ideas?


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OK, since posting this I have a little info more about this prob. Typically when it occurs, it does so about 8-9mins into my drive. Does something occur about 8-9 minutes after starting a car and driving it? Is it related to the car getting up to normal operating temperature or something like that?

 

I'll be watching this one... I've got a very similar problem too. bump ^

 

This will sound very strange but I had a similiar problem on my 94 and it was a fuel ventilation problem. I was getting a sort of "vapor lock" in my fuel system and so I was starving the motor. Its a long shot because you have tested your fuel pressure but worth a shot checking it out. Just next time it starts to act up, pull over and remove your gas cap, if you hear a loud hissing sound and the car runs fine again thats it and trouble shoot from there. Like I said its a long shot because you already troubleshot the fuel but.... thats all i got man. Good luck with whatever it is!

 

The problem is that I don't have time to do much of anything when it happens. Sometimes, I don't even have enough time to get out of the throttle before the things refires and starts running again.

 

i had a simular problem to that with my car. I took it to 6 different shops and no one could tell me what was wrong. Then one day i happend to see a broken ground wire, i reconnected it and everything was solved. What was happening was that it would ground out shocking the computer and the computer would cut off and the it would come back and everything would be fine.

 

Please see the update above...

 

I was guessing ground wire like stated earlier. The 8-9 minute time frame is interesting. A bad ground would do it whenever.