I need to draw upon the broad experience base here at the z-28.com site...I think I've got a very unusual problem here...I just bought a '93 corvette from my father-in-law...It's a 180,000 mile original drivetrain car. He's had a number of problems lately & has been taking it back & forth to the dealer, got tired of that & sold it to me....Here's the chronology: had problems with hard start/poor fuel mileage...Replaced the opti-spark...Car cut off, would not start..replaced the fuel pump. Car ran fine for a while, then would not start....Took it to the dealer, they did all of their "electrical" checks and found nothing.....They checked the fuel pressure & said it was good...they suggested that maybe the timing chain jumped time....He pulled it from the dealer and it sat for a few months until he sold it....

When I received the car, I replaced the battery, and fired it up...It idled EXTREMELY rough. And if I give it gas, it dies right away. When it does die, it kind of diesels until it finally dies. The exaust smells like pure gas. No codes come up on the computer.

I started [to be safe] by replacing the timing chain. There was a good amount of slop, but it did not jump time.
Next I checked the TPS sensor, AT THE SENSOR the voltage was .6 V at 0% and 4.05 V at WOT.

What have you all seen in the past? Where should I go next???

I really want to get this beast on the road! Any help would sure be appreciated!!!!!

 

it could be the icm, my 93z did that, it would start up but as soon as i gave it some fuel it would die every time

 

I'd replace the Coil and the ICM since the opti and fuel pump have already been replaced...

 

The other thing I noticed was that there is a loud hissing sound coming from the air cleaner...almost like there's some type of leak...I checked the MAP sensor, it's good. Engine vacuum is at 10 " ...I don't know if that means there's a leak or it's due to the poor idle. I pinched off all of the engine vacuum hoses one by one and none made a difference..

 

It definitely seems like a vacuum issue to me. Its usually a telltale sign when you give it gas and it dies. How do you know the MAP sensor is good? Also check your fuel injectors, maybe they are leaky or bad. A compression test is quick and easy and might tell you something too. HTH

 

I believe the map sensor is good because I checked the voltage output of the sensor at atmosphere & I applied 20 " hg to it, and the two voltage outputs were correct according to the manual, and the response was quick....

Where else could I have a vacuum leak? I plugged all the hoses and nothing made a difference.... I manually moved the EGR and it was fully seated, when I moved it the engine died....

Any thoughts?

 

You could try idling the car and spray some WD-40 in the engine bay to find the vacuum leak. If the engine idles up real quick when you spray the WD-40, then there's a vacuum leak in that area. Other than that, I don't know.