So i have a 99 Mustang GT that doesnt idle right. Everytime i first start it it revs to abut 1000 but than drops down to 100 and sometimes dies. It will keep bouncing like that until i hold it on 2000 rpm. I just bought the car so i dont know much about it.

 

manudevil20:

Clean the IAC (idle air control) valve first. It's the little silver can with an electrical plug on it hanging off the upper plenum (or, just in front of the Pony plate). Remove the IAC being careful not to tear the gasket. Use carb cleaner and tap the IAC on the workbench after spraying. Repeat until the flow of brown stuff stops. This should greatly improve idle performance. There are many threads on Mustang boards about the IAC and idle problems so you can search and see what others have done. I suggest replacing the old one (eventually, you'll need one)with anOEM Ford IAC because it is a critical item (imho).

You can also clean the MAF wires (be really careful because they are brittle and very fine diameter). Use MAF cleaner or isopropyl alcohol and a Q-Tip. Again, be very careful. If you bust a wire, you have to buy a new MAF ($$).

Check the PCV valve still rattles easily. If it doesn't, replace it (it's cheap).

Tend to the IAC first and then the other things if idle stability is still a problem.

Please post your mods, it helps to know if the car is stock or not.

HTH,

Chris

 

Ok i will try that. Just to make sure the IAC Valve is the one sitting right next to the throttle body on top of the Intake Manifold? Sorry about not posting mods. It is stock for now