View Full Version : Surging at Idel

02-25-2009, 07:08 PM
I just bought a 04 Mystic Vert with a Kenne Bell 2.2, yesterday I noticed sitting at a light the idel was surging up to around 1000 then it would go back to around 850. Any ideas????

02-26-2009, 08:38 PM
TPS or throttle position sensor.

03-06-2009, 08:11 AM

I turned off the windshield defrost and the surging went away.

03-06-2009, 11:30 PM
That's weird! :scratch:

RF Cobra
03-07-2009, 12:01 AM
Sounds like an electrical problem.

The Fox body Stangs and TBirds had ignition switches that were prone to failure and they would cause all sorts of weird electrical problems when they went bad.

03-09-2009, 08:51 PM

Everythine else seems to work, don't know for sure though, still getting used to the car. It's starting to get hot outside have to turn on the AC and see what happens.

03-12-2009, 10:52 PM
check the volt output of the alternator it should be around 14V and if that is good load test the battary if that is all good then it a wiring proplem. hope this helps

05-24-2009, 10:05 AM
Considering the supercharger configuration, the tune may have corrupt the load tables or parameters used to regulate idel when the AC is active. If this has been a recurring problem, Could be an easy fix by clearing the EEPROM memory (disconnect battery for 30 minutes). It sounds like the IAC valve is attempting to provide correct air bleed to maintain idle but it seems to overshoot causing the surge. It is possible that the IAC valve needs to be replaced if the internal springs are damaged to allow for valve return. It may be possibe to clean the IAC valve as long as you hold the solenoid part up to prevent any solvents from entering the valve motor through the pintle shaft. Electrical parts cleaner could be used but that would remove any lubricants on the internal parts. If the valve is gummed up that would cause the response to become slow resulting in the surge. If the valve looks clean, the EEPROM clearing may cure the issue.

Uncontrollable surge: Usually caused by intake gasket seal leak (could be throttle body seal, lower plenum seal, blower port seal or leaking PCV valve cover gasket seal leak), or can be caused by the EGR system.

Is the throttle body the oval type or dual port style? I do recall some of the oval designs had some problems with the IAC port. (not sure what the issues were but could be what you are experiencing).

05-24-2009, 10:08 AM
Then again, 850 to 1000 RPM is within normal spec unles it is oscillating between the two speeds. Problematic IAC surges will swing up to 1500 to 2500. If that is the case, then you need to do something to correct it.

05-24-2009, 04:19 PM
I had the same problem so I cleaned my IAC with some carb cleaner and cotton swabs, it fixed the problem right away.