Revs / Idle problem

[RoShamBo]

When I start the car up in the morning it revs itself up to just under 2k revs then drops down to normal revs - does anyone know what this might be ? I dont go near the throttle when starting.
A local specialist suggests MAF or Oxygen sensors. An associated problem (I think) is when pulling away in a lower gear than maybe normal (example is going over speed bumps in second gear at around 3-4 miles an hour - or a rolling start in second gear) the revs drop then bounce back up. This can make driving in traffic a little jerky.
Its a 98 996 with 35,000 miles on it & I know idle on earlier cars is altered by the aircon - but either on or off the revs seem to drop down quite a bit then back up before settling.

Any ideas ?

Julian.

[McP]

Mine does the same. I remember that my 2.5 Boxster used to do this also and that it was due to a quirk with the engine management system. I'll see if I can find the thread for the Boxster problem.

>> Edited by McP on Tuesday 25th November 12:18

[argonaut]

If you get fluctuating idle speeds at rest, or more commonly when coming to a stop - that's likely to be the mass airflow sensor or something!

Anyway - needs to be replaced. Had it done myself - not TOO expensive.