jussagt

Okay guys.. to start.. Its a 99 Stang GT. (4.6L SOHC) The car has BBK Long tube headers, X-pipe, MSD Ignition, CAI, Under-drive Pulleys, Stage II Clutch, Steeda Short-throw shifter.. everything else is believed to be stock on the car.

The car used to hesitate at idle and jump up and down and sometimes get so low that it would stall. Also, if I rev the engine up.. the engine wants to stay there for a few seconds before climbing back down.

I first tried Idle Air Control Sensor, this didn't change anything.

I changed the Air Charge Temperature Sensor & Cleaned out the entire throttle body.
-this seemed to have stopped the fluctuation at idle but..

The car still climbs rpms and stays there a few seconds before coming back down, as well as imbetween shifts.. the car wants to stay at those rpms with out free-falling. As well if your just cruising down the street and put it in neutral, the cars rpm's bounces up and down between 1000 - 1500rpms until you come to a stop and/or put it in gear.

What sounds to be the issue? Vacuum leak? Suckin air somewhere? EGR fault?

Thanks in advance for you inputs!

NaughtyGeek

Did you change the ISC Valve or the TPS? If it was the ISC Valve, did you disconnect the battery after you changed it to reset the PCM? It does sound like you're sucking air but you would likely get a CEL if you were.

SVTeeshirt

You said you did the IAC... was it replaced? because cliffy will tell you; actually ford will but he will tell you ford tells you(lol) that it can't be cleaned. Stalling, my car used to stall whenever i pushed the clutch in untill i replaced the mass air flow sensor(mostly slowing down from high speeds such as interstate to an offramp etc etc.). Could be a few things.