i have a 89 camaro iroc. what it does is starts and cuts off in 15- 20 mins like if someone turn the key off. i have replace almost every part on this car from fuel pump to computer, module ,distubutor, iac value....i taken this car to several shop with no results. the last shop suggust to replace the wire horness. what do you think?

Reads like an electrial connection is heating up and providing a high resistance.

Check symptoms of the shutoff - if it shuts off quickly/cleanly, then I'd suggest looking in the ignition system. If it stumbles alittle at shutdown, I'd look at the fuel system.

You now know where to look for electrical connections. Carry along a test light or meter, and if possible, when the car shuts down, leave the key on and check for HEI voltage, fuel relay voltage, etc. Somewhere, there is a power loss.

Might even look at the solenoid terminal stud and check those fusible links to make sure they are in good repair. Any connection you feel hot to the touch, problem is right there.

Could even be a bad power relay for the fuel injectors, ignition switch, high resistance ground.

One needs patience and a methodical plan.

Yeah, we need more info.

Does the car always restart immediately?

Were the shops you taken to able to reproduce the problem? I would think that when the failure is present, it wouldn't take much to determine if it was a fuel or ignition issue.

Do you get a Check Engine light before it stalls? The next time it starts, run an engine diagnostic check to see if there are any trouble codes present. This doesn't tell everything but, it might narrow down the problem.