Martin5.0

I have a 91 LX and did a 5.0 Conversion. It was a 4 Cylinder car. I am haveing this same issue. The motor is a stock 5.0 out of a 91 GT. I tried to clean the IAC and it didnt do much. I have not done much to it since then. Anyone out there care to help me out . Im new to the Mustang scene.

MADMAC

I have a 94 GT and have the same problem. Hanging at 2300 to 2500 between shifts then drop down. Mine has something to with the ECM. When I disconnect the IAC I stops the Idle run up. (IAC is clean and new). People have told me that it is normal for my car. I don't think so. because other 94/95's don't do it. I was told to disconnect one of the switches to my clutch pedal and reset the ECM. it doesn't help either. I am going to purchase a PMS in the near future and see if it will correct it outside of replacing the ECM. I am always open for other ideas.

USMC1775

Its the dashpot function of the computer. Its supposed to hang a bit until you come to a complete stop.

calinotch

you sure? mine didnt do it before i had to smog it.

MADMAC

I understand the dashpot function, but not hanging at 2500 RPM. Way too much. For the time being I have disconnected it and adjusted the idle air speed on the throttle body to 850 RPM. I just don't run the defrost/AC at a stop light. I was thinking about rigging up a small switch to engage it when I need it, like at intial warm up or running A/C during summer.

CALINOATCH, have tried disconnecting your battery and reset ECM on yours. May or may not help but worth a try. It didn't work on mine though.