Jerpitcher

Hey everyone, I'm in need of some help yet again...haha...well the problem this time is that at idle speed about 500 rpm the engine is running really rough and has died a few times. Driving it runs fine, just at idle does it have a problem. We had the fuel pump checked out and they said the fuel pressure was fine. Any ideas? Thanks for the help!

jetech

Is your engine stock? I believe the spec for the stock emissions car at idle with vac adv disconnected is 500 rpm but I think any engine mod's change this. When I removed the EGR and installed a manifold and cam I had to bump my idle up to 750 rpm. Even with the stock setup the engine may like 600 to 750 rpm, might be worth a try. :smash: :cheers:

Jerpitcher

The engine is stock...we've replaced the water pump, and the compressor for the a/c. It hasn't done this before and we've always had the idle speed set at 500, so I'm not sure...

jerryp58

If that's 500 RPM in Drive, that's correct.

Was the AC compressor hooked up before? If not, the current idle speed might not be enough to handle the extra load.

jerryp58

Here are the idle numbers out of my 1977 Corvette Specifications booklet (FREE from Chevy by calling 800-222-1020)...

...........................L48.....L82
manual trans........800.....900
auto trans in D.....600.....700


[Modified by jerryp58, 4:26 PM 8/23/2003]

bigvette1

Check these out to see where you are at.

1. Hook up a vacuum gauge to manifold vacuum. Stock shoul,d be 16-18" and pretty steady. If not look and listen for a vacuum leak around the carb, hoses etc.

2. Hook up the timing light, plug the vacuum advance and what is your base timing and is it steady?

3. Pinch off the big vacuum line at the back of the intake manifold that goes to the vacuum system of the car - headlights etc. See if the idle stablizes.

4. Hows the tune up situation with the car? Air filter, fuel filter etc.

Check out the basic before adjusting things on the car.

Jerpitcher

Ok, thanks for the suggestions everyone...I don't have much equipment with me here at school, but i'll check what I can...and yeah, we've had the compressor on for a while and it ran fine. Thanks again everyone, I appreciate the help....this is a great forum!

Jerpitcher

Well, I tried all the vacuum lines and none of them worked...still havin the problem

Bobchad

Is this with or without the a/c. I think there is an idle step up circuit that allows either for a slightly faster idle or better maintains the 500 rpm idle on these cars.

Jerpitcher

This is with the a/c both on and off...the idle is worse when the a/c is on though and could potentially die...