I have been working on this all weekend and can't figure it out.

I've got a '94 Z28 auto. When I turn the key sometimes it will be fine and I'll start it and then the engine revs up and down and goes crazy until it shuts off. Other times I turn the key on and the computer just keeps resetting to where I hear the fuel pump prime or the fans flicker on and off.

I don't know enough about which wire might be the culprit so it seems like I just keep going in circles. I have the dash apart and nearly out so I can get to all the wiring. It's not in the ignition switch or the connector because I had it plugged in downstream of that on manual switches and it still did it. I replaced the pcm with a spare and that's not it. I checked in the engine compartment and it doesn't seem to be any of the main power or grounds. It really seems like it's on the driver side under dash. When I start messing in there is when I seem to get it to act up the most.

I unplugged the blue connector from the pcm and it still started up and had a problem so I'm pretty sure it's not in the group of wiring.

I need to figure out what wires in there could cause such a problem so that I know where to start testing and how to test them.

Also, what is the big black thing that all the wires go into and then out of and up to the fuse box? Nothing seems to actually plug in it just looks like the wires run through it and then to the fuse box. Does that come apart?

Anyway, I need all the help I can get right now. I've been at it since 2pm-1am sat. and 9am-1am sunday and don't seem to be any further.

What to check and how to check it would be the best way to help right now so that I can just try something different I haven't tried yet.

Thanks,
Ross

 

Is your security light on the dash flashing or doing anything funny? The VATS (vehicle anti theft system) can disable the fuel pump if it doesn't read the right resistance from the black resistor in your ignition key. There is a separate module for the VATS system and sometimes it can go bad causing some weird problems. Most of the time the problem ends up being a no start condition though.

Good luck.

 

Forgot to mention, I have VATS programmed out.. also swapped the box just for kicks, bypassed it at the relay, and swapped the relay, no difference. This is definately a short or corrupted wire somewhere as it's very intermittent and randomly happening. Fans sometimes halfway kick on and off, the fuel pump primes at random intervals and lengths of time. Whatever feeds the signal to do all these events is shorted and causing them to happen too long or shrot and repeatedly instead of once when the car comes on. Possibly like a ground or power to the pcm itself so it keeps resetting.

 

Put a meter or test light at a convenient place downstream while you are messing with the wiring that seems to cause the trouble.

 

that's the problem.. can't find a place downstream...or can't tell what goes to what in the fuse box

Although I think just now I figured the bad wire is for sure in that box thing right near the fuse box. http://members.***.net/pitrepix/site...switch/005.jpg
It's that thing on the left. Anyone know what exactly that is or how to get it apart? I seperated the wires a little in there and the car just went awol when I did that. The short has to be in a wire right in that or going into it. I need to get it apart so I can find where the wires run to and also so I can put new wires in.

 

Sorry, your pic is not big or detailed enough for me to know what you are referring to.

 

nevermind figured that part out.. think it's something else now.