cleanupman

I was wondering what would cause idle issue like constant idle change from 1500 rpms to 1300 rpms and also when I'm at a complete stop just all of a sudden go thru the roof as if I am slamming on the gas. I was thinking a leak in the intake manifold be I'm not mechanic I could use some help.

jboggs_23

I would check your egr valve but I don't think it would be revving higher, buy mine did miss at idle because of that.what year I'd your sting.

cleanupman

it's a 1991 ford mustang gt

cleanupman

would I pop a code if I had a bad egr valve I check my codes and nothing pops.

dawson1112

Start by pulling your Idle Air Control and cleaning it. If it were a egr problem your idle would be very erratic and it would either stall or act like it wants to stall. A vacuum leak in the intake would likely cause a constant high idle , while a vacuum line that is cracked may cause it to surge or hunt idle. My guess is you either have a faulty IAC or it just needs to be cleaned . While your at it a good throttle body cleaning wouldn't hurt either.

darkmach1

3 steps:

1: find and fix vacuum leaks
2: clean/ change (I vote change) IAC and TPS
3. Idle reset procedure