cold start high revs

[Rp23g7]

1994 MK8, 116,000 miles,

when starting cold first thing in the morning, it revs really high, without touching the accelerator pedal. cant be good for all the non oiled mechanical stuff. slight stumble off idle when cold too. Vacuum leak? runs fine when warm. doing a whole tune up soon, IAC and TPS etc getting replaced, maybe that will solve it.

 

[driller]

Notwithstanding a vacuum leak, it sounds typical of an Idle Air Control Valve issue. Note that the manual states the Idle Air Control Valve cannot be cleaned and must be replaced.

The Idle Air Control Valve on the Gen1's are a PITA to access. I've found removal of the cowl and/or the throttle body the best way to gain access to it. PRO TIP: To prevent dropping materials into the intake manifold, tape off and/or stuff openings with a rag.

Be sure to clear the KAM(Keep Alive Memory) after replacing the Idle Air Control Valve. This will allow the PCM to recalibrate idle accordingly. To clear the KAM, disconnect the NEGATIVE battery cable (only) for at least 5 minutes.

Follow these steps to complete an Idle Relearn after clearing KAM:

1. With vehicle at a complete stop, set the parking brake.
2. Put gear shifter in "P" (Park), turn off all accessories.
3. Run the engine until it reaches normal operating temperature.
4. Allow engine to idle for at least one minute.
5. Turn the air conditioning on and allow the engine to idle for at least one minute.
6. Release the parking brake. With your foot on the brake pedal and the A/C still on, put the vehicle in "D" (Drive) and allow the engine to idle for at least one minute.
7. Drive the vehicle to complete the relearning process. Just make sure you drive easy for the first 30 miles, so the PCM can re-learn and adapt to your driving style.