jadavis1992

I have a 91 mustang with a mostly stock 5.0 only has headers and exhaust. In the morning when i am going to work i hop in the car and it starts right up then dies or almost dies. If it does not die it surges and then the idle levels out but is still rough and if i hit the gas it falls on its face and surges ,untill about 30 seconds when it seems it seems to run fine.

1ATony

You may want to replace the IAC valve on it,a bad IAC which is a common thing to go bad on these mustangs,would cause those symptoms.

If that does not resolve the issue it may also be a bad EGR valve. A bad EGR valve would also cause your ford mustang to stall.Another symptom of a bad EGR valve is if you come to a stop at a set of lights or a stop sign and the car leaps forward a bad EGR would cause those symptoms too.

Bubba 95SN

Run EEC tests if EGR has problem you will get a code for EVP. Take a old toothbrush and some dish detergent and water 50/50 clean throttle body, wipe out goo. Try cleaning the air bypass valve some carb cleaner will work. Disconnect negative battery terminal for 5 minutes. Start car let run for a minute, then drop in gear, operate a/c. Should relearn to idle. Now drive. First 15 miles may act a little strange as computer relearns-adapts. Bubba