Sho still cuts off and on sometimes. Any ideas? Need help!

[chrism3784]

After all the things I replaced and checked, it still does it! It'll drive fine most the time. Once in a while, the engine will complete cut off and immediately kick back on and run. Sometimes it sputters as it cuts on and off on and off. Every now and then when it does it, the check engine light flashes on when its screwing up, then goes off immediately when firing again. Its driving me nuts.

I swapped cam sensor, 3 different DIS's, completely replaced crank sensor and gapped correctly, and swapped coil packs. All doing the same. I also changed all plug wires, check each spark plug, and swapped out the ECU, there all good. I also checked that red/light-green wire from the ign switch that power up the ignition system. Connected a bulb to it, took on drive. When car started bucking and doing it, light stayed completely lit, showing its not that. It seems to do it mostly during heavy acceleration. But it can at any time.

Also, when its screwing up, the tach still works, so that means it not the crank sensor?

 

[sho pleaser]

mine did that to but i changed the fuel pump sending unit and tank and its been fine for about 3 months now the only thing i came up with was the pump was weak and get hot but also if i let the car sit overnight and start it in the morning it took 2 trys to start but was fine the rest of the day than

 

[eLindemann]

It is often said that the tach not working is associated with the crank sensor, but mine shut off when my CID malfunctioned - so take it that its either one or the other.

I would replace the fuel filter, cheap potential fix. When I bought my SHO the fuel filter was all gunked up and causing the engine to cut out.

 

[SHOtime2511]

whats the deal with the IAC?

 

[rubydist]

Also, when its screwing up, the tach still works, so that means it not the crank sensor?

That is incorrect - the tach is driven by the cam sensor and the dis, so the tach working tells you nothing about the crank sensor.

Have you pulled the codes recently? There may not be any, but there might be something to help you.

Have you changed the tps? Your symptoms could be caused by a flaky tps. Also, you could have a bad connection or circuit on the mafs/tps/iat circuit - I would check all that wiring very carefully.

 

[Art5]

I had the same problem when I had my 92 and then I just crashed the car, because couldn't accelarate when it started fishtailing.

 

[Vnuk1]

I had this exact issue check the wires on the black distribution block on the firewall on the drivers side. Mine were corroded and only a few wires were connceted and that was what caused the shutting off and immediately turning back on. Might be your problem as well..

 

[chrism3784]

Mine doesn't have that black box, mines 90 style. That wasn't till 92. The wiring seems ok, and the wire that turns on all the sensors and such is working fine.

Crank sensors brand new. When I changed it, still did the same exact thing. As far as I can see and what I saw when I changed it is the water pump isn't leaking, thats new to.

Could be getting somewhere with the fuel pump. Would it cause the check engine light to flash on for the second it cuts off? There a check engine sensor for low fuel pressure or something?

 

[VortecGT]

Put a fuel pressure gauge on it and drive it around. See if it fluctuates (more or less than it should)

 

[sho pleaser]

be for i did mine i checked the pressure and it was 32 psi running than off it was 25 check it be for u park it for the night off dont forget the psi than first thing in the morn check it before tryn to start see if it is the same when u parked it i think when the car is running it should be at 36 or higher the check engine light was on on mine and was lean and had fuel pump cir. to low and a ground prob all fuel related

 

[chrism3784]

I'm begining to think its fuel now. I drove it on interstate and for most part drives fine. When I downshift and step on it, it doesn't cut off, just lags really bad. What I though was just plain cutting off and not firing is just lagging. I'd hold the gas down and would slowly accelerate and sometimes catch for a bit good, then slow again. but normal driving is fine, when I take off hard it cuts off and on real bad, guess fuel pressure really drops.

I know for a fact the fuel pump was going a few years ago, a few times with the 3.8 in it I had a hard time starting it, and it made wierd winding noise, then quit. Been fine since then. It has the same fuel pump since the 3.8, since 1988. Prob not a bad idea to change anyways, probably not pumping the pressure needed for an sho engine.