Well for the past few months my car has been surging when I am at idle. The car is a 94 auto and so I got it scanned and the only thing that the mechanic noticed was when the car would surge the IAC count would jump from a constant of 3 to 40 and then back to 3. The car runs good, I drive it everyday and no check engine light is on. Basically the car idles at 500 when it is warmed up sometimes it will surge up to 750 or 1000, just like you tapped the gas, I already tried a new IAC and it did not help. Any help is appreciated.

 

Did you add any mods that might have caused this change? My tuner tuned out idle surge that occurred during open loop, cold engine conditions on my engine.

 

No major mods besides bolt ons

 

Boltons include a TB? the aftermarket TBs often need some tweaking.

 

No, no TB, pretty much stock, the car was running great with no problems and then this happen more and more over the past six months, like the car idles and then starts to idle a little rough and then it surges up.