Hello everyone. I am a new member in the middle of trying to figure out what’s wrong with my C4 (1990, 6spd.) I will give a rundown of what has happened, if you have any ideas or have experienced this yourself your input would be greatly appreciated.

Approximately 20 mins into my drive to work last week my Vette suddenly cut out almost to the point of stalling when I stepped on the gas. If I barely touched the peddle it would maintain speed but if I pressed down more then about a 1/4 of an inch the engine would almost completely stall out.

I got my car home and did a fuel pressure test off the fuel rail and the fuel pressure was at spec based on the books I have. As I was testing the fuel pressure I noticed that the engine was stumbling less as I pressed the pedal. I unhooked the gauge shut the hood and went for a ride. All was well, I went a few miles and came home. The car was running strong. I checked things over on the engine and all looked ok so I decided to go out for another spin to see if any of the symptoms that were occurring earlier would happen again. This time I fired the car back up, backed up on the road and the engine started cutting out again as soon as I touched the pedal.

I'm at a loss. The fuel filter, plugs, wires, cap, rotor ande O2 sensor were changed approximatly 400 miles ago. I don't see or hear any signs of a vaccum leak but I haven't actually tested vaccum. My thoughts are it's either a vaccum issue, a fuel pump problem (bad pump, badd connection etc.) or possibly a plugged cat.

What do you all think? The fact that it started working ok then stopped again has me puzzled and thinking maybe a bum connection to the fuel pump.

Thank you for your time.

 

Hmm maybe shifting debris in the fuel filter either that or a vaccum leak? Goldcylon

 

Sounds like it could be Throttle Pos. Switch.
If you have a multi-meter, you can check to see if it is working correctly. The FSM explains it....

 

Are there any codes to go by (SES light on)? Could be many things. TPS, MAF, EGR, dirty TB, vac leak....

 

I think you picked a good starting point with the fuel. But I would not get away from it yet. You are going need to make those checks when the problem is really happening. Clogged filters usually give consistent problems and will usually have an effect at the higher speeds.

A bad fuel pump can give you pressures all over the place. You might want to hang the gauge out of the hood and drive for a while. There could be debris in the tank causing the sock to clog at times. You can pull out the assembly and look in the tank and check the sock.

The TPS should be easy to check by monitoring the 0 - 5 volts out and moving the pedal.

 

Its A Plugged Cat. Mine Did The Same Thing. Just Unhook You Cats At The Header And Take It For A Spin ,i Bet You Will Find That This Was Your Problem.

 

I really appreciate everyone taking the time to post responses and suggestions. As soon as I can I'll be back out in the garage checking everything out.

I will post what I find out.

Thank you again!

Bill-



I just came back from the Garage and it looks like I have the same issue you had GARVETTE91! I pulled the CAT and everything behind it off the car and she runs like a beast! (A real loud beast) She really ran fantastic! So time to order a CAT and possibly a new system. I'm going to look around the forums to see which systems people seem to like.

Thank you all again very much for your help!

Bill

 

ok;
first, if it's a fuel pump, it won't even idle
second, it could be a throttle position sensor
third, yea it could be a fuel filter, but if it sits like 20 minutes, the fuel
pump pressure will fill the filter, and it will fun good like 10-12
minutes unless you get on it because it will run out of fuel again
4th, it could be the fuel pressure regulator bypassing fuel with a bad
diaphragm
5th it could be a bad fuel pump relay in addition to a bad oil
pressure switch (the alternate method to get the fuel pump
started)
6th It could be a intermittant ignition switch
7th bad ground anywhere

good luck