Okay here it is, my car starts normal and stuff like that, but after it's warmed up, the idle goes up and down, up and down between 750 & the 500 rpm mark. The last owner told me he took it to a mech and said it was because of the old rusty exhaust that's still on the car. The exhaust does have a hole in the y-pipe right where the two pipes converge into the cat. My question is, does it idle funny because of the exhaust or do i have a vacuum leak. your help is greatly appreciated. thanx

the new guy

 

only thing the ypipe would affect is noise hehe.

probably vacuum related. go here for some ideas:

http://www.k2rd.com/FC3S/faq.html

good luck
brandon

 

Howdy!
I had a similar problem. My '91 would idle @ 1300 RPM until my temp gauge hit halfway, then it would idle @ 200-600 RPM. Check the screw on top of your upper manifold, right above where it says "13B Injection." It is the "idle speed screw". Try unscrewing it w/ your engine running, a little at a time. I did this, and now it idles @ 1100 RPM. If this dosen't work, it could either by your thermowax or a compression problem. Check www.fc3s.org. They have Factory Service Manuals in PDF format. Page by page, w/ pictures on how to check for these problems!!

Good Luck!
Rick Novak