Pontiac Repair: rough idle, valve cover gasket, vacuum leak

Question
1989 pontiac grand am le idles rough like it has a miss. sometimes it will idle good. runs good just rough idle. plugs and wires changed. i had my egr valve off while replacing my valve cover gasket and i shook the egr valve and something in it rattled, is that okay? thanks for your help!

Answer
Hey Gary:

A vacuum leak can cause a rough idle and the leak can be from the EGR valve. The rattle noise you heard could be carbon loose in the valve or something in the diaphram ratteling around. with the engine running see if the diaphram is lifted up and the valve is applied. you can also lift up on it with your fingers and see if the idle changes and then smoothes out. It can be sticking open. That 2.5 liter engine was noted for an erratic idle or a hunting idle. It was pretty much normal operation as long as it doesn't hunt by more than maybe 25 rpm's.. good luck :}