*GMMerlin*89 GMC Rough Idle and Stalling

[astralepic]

Hey GMMerlin, I got a vacuum gauge and hooked up to the vacuum line that went to the break booster. I figured this was good considering that it led directly to the intake manfold as you mentioned in your post. The vacuum at idle was about 20psi. It was consistent, barely moving at all. The manual that came with the gauge said to run the motor up to about 2000 rpm. I did this and the vacuum dropped to about 10psi. The motor was cold and I did not run it long enough to get it warm. It's pretty cold here right now, highs in the mid 30's. Do you think this is an issue? The manual said something was wrong with the exhaust system, but I really don't feel that's the case considering it was replaced about 3 years ago. Everything was new except the headers. New cat, muffler and all pipes.

Also, something I noticed never before was a noise under the hood. Are there bearings in the distributor? I assume so and I think one may be bad. Something around the area of the dist. was making a noise which reminded me of a bearing going bad. What are you thoughts?

As always, thanks big time for your help. We are close and I couldn't feel more confident that it's something small without your assistance.

[DEEPEE]

I have the SAME EXACT INDENTICAL PROBLEM. Idles good cold, after a good warm up....surges sitting at a stop with rpm's fluctuating. Runs great after leaving the stop. Thought I would try and kick start this post again to see if someone knows what cause this. It's more annoying than anything especially with the magnaflow and turn downs underneath. MERLIN, can you check into this for us? I've replaced my IAC valve and checked for intake leaks. Didn't really want to start just changing parts. $$$$$$$$ Someone told me it could be the computer. $$$$$$$ Has anyone found the problem and cured it? Please let us know.

[DEEPEE]

Forgot to mention, mine is a 5.7l 1999.

[astralepic]

My issue was the distributor. The actual issue delt with a shim at the base of the distributor which controls advanced timing. Try it and let me know. Remember though, mine is a 93 model. I imagine there's a difference, but don't know enough about newer models. Good luck!