jpl617

I have a 87 mustang gt 5.0 high output. When i start the engine the rpms go down to about eight hundred and sounds like it wants to die then they shoot up to about 1300...

Any ideas on what could be the problem and the solution?

Airoyster

Funny! I just corrected this problem on my car yesterday morning! The issue is your IAC valve on the intake.Apparently it's a common problem,but can easily be corrected with a cleaning. Disconnect your negative battery terminal,unplug the lead from the IAC valve and then remove the two 8mm bolts that hold it in place.Flush out the valve assembly with carb cleaner to remove the carbon deposits.I actually filled it with carb cleaner,let it sit for a couple of minutes and then emptied it and blasted it again to make sure it was clean.I then used some Seafoam Deep Creep for a final rinse.(regular sea foam will work too...its the same stuff,just not in spray form). Bolt the valve back on the intake,plug it in,reconnect your battery terminal,and you're done. You should see an instant improvement in the idle.Your car may or may not puff a little white smoke as the cleaner residue gets sucked through the intake,but thats normal.I was informed that running a bottle of Seafoam engine treatment through my gas tank 2-3 times year will eliminate this problem from ever happening again.