Hi all,
well.... this is a weird one. The 90 c4 will run like a scalded ape one time, the next it runs like it is starving for fuel. I had to have it towed home yesterday; it left me dead in the store parking lot. Today it started right up and runs fine, smooth as silk. Turn it off for 1/2 hour or so and it will start up, but runs like 4 of the plug wires are pulled. You can't touch the gas at all or it will die. It will idle but very badly. Turn it off and wait a day and it runs fine again.

I have replaced the plugs, wires, cap, rotor, fuel filter, oil, oil filter, air cleaner (k&n), idler, serp. Belt, and..... filled it with 91 gas with a bottle of 7 point oct. booster. Fuel inj. cleaner. Short of removing the radiator cap and driving a new Vette under it, I’m at a loss to know what's going on here. Anybody ever have this happen to them before, or is my Vette gone mad?

Could the computer be going **** up? It was scanned and didn't throw any codes. Someone told me the ign. module might be going bad. Would it run one time and not the other with that going out? When it is acting up it will start up and die off. After a while it will start up and idle poorly, but die off if you even think of touching the gas. This car has always ran very good, it is in great shape and well taken care of.

Any help would be great,
Gregg

 

i'm concidering changing out the computer and eprom next. and maybe the whole distributer. what do you think????

 

It sounds like a fuel pump to me. Hook-up a gauge to the schrader valve on the fuel rail and check the pressure from idle on up. Good luck and let us know what you find. Oh yeah, if you don't have a gauge you can spray carb cleaner into the throttle body while the engine is running, if the engine speeds up and runs better it's a fuel problem.

 

I have a 90 coupe and I had the same problem. I ended up taking it to the dealership and it was the injectors. I live in laguna niguel CA so if you want i can drive down and help you figure this out. Let me know

 

I had simialr problems with my 90,I replaced everything as well come to find out it was the ECM....replaced it and haven't had any problems yet.


Jason

 

I had a catalytic converter break up and sent pieces down the pipe that would turn and plug the pipe up sometimes, lose power barely idle. Next time I would start it, it would turn a different way, run normal until it moved around again. I installed a 10psi pressure gauge at the exhaust manifold ( removed the air injector check valve), it should never go above 2 psi ( I think), mine was going over 10 psi, but only when it was acting up. A clue that the cat is breaking up; there is a rattling sound under the car when idling. I smacked the cat with a pipe with the engine off, and it sounded exactly like the rattle I heard when it idled. Try the pressure gauge. It's a cheap check.

I'll bet money, it's not the computer. In fact, why don't you buy mine, I didn't need it. Has zero miles on it? I can't take it back.
Mike

 

the cats are good. just had them checked out when they hung the new exhaust a few months ago. what do you want for the ecm?

i went out this morning and it fired right up again. ran perfect. yesterday i ran it for a straight hour in the driveway. ran perfect. drove it down the street and back a few times...perfect. parked it in the garage, waited about an hour.... crap, hardly ran at all. would die if you touched the gas at all. this afternoon....it's fine again. seems like as long as it is running good it will stay good. just don't turn it off for a while and try to go again.

the general servey is leaning toward the ecm.

i will try the suggested ideas thursday after work. until then.....

thanks all,
gregg

 

I had the same problem on my 90 and it was the ECM.

The ECM gets cooked by the headers when you shut down. Heat rises and under hood ventilation is poor. Whenever I can, I pop the hood when I park it. I figure that the less heat soaks the ECM is put through the better.