Start up RPM

[kcorybrian]

I have a 1999 996 and am experiencing an engine idle issue when the car is warm. On a cold start, it reaches and holds its start up RPM with no issues. When I start the car when warm it hunts for the correct idle for 5 - 10 seconds varying rpm by around 200-300 rpm.

This started after a recent battery change. My Porsche mechanic has checked the fault codes (which were fine) and suggests that it should correct the issue on its own. Any ideas?

[1999Porsche911]

I have a 1999 996 and am experiencing an engine idle issue when the car is warm. On a cold start, it reaches and holds its start up RPM with no issues. When I start the car when warm it hunts for the correct idle for 5 - 10 seconds varying rpm by around 200-300 rpm.

This started after a recent battery change. My Porsche mechanic has checked the fault codes (which were fine) and suggests that it should correct the issue on its own. Any ideas?

The 99 will take a few drive cycles to completely reset the computer and it should idle fine then, If not, could be a vaccum line is off or a dirty MAF which can easily be cleaned.

[nick49]

Sounds a little like MAF sensor may be faulty. If idle is irregular when engine is warm like when stopped at a light and this happens more often than not, I would bet that sensor needs replacement. Seems like cleaning is a temporary solution to a reoccuring problem, whereas replacement is more permanent. Been there!

[kcorybrian]

Thanks for both of your replies. I am hoping it clears up after a few more cycles.

I have started the car at least 10 times over the last few days and it is still hunting for the correct idle if the engine is warm. Once it finds the correct idle (10 seconds or so later) it runs perfectly. When I start it cold there is no problem.

Could the MAF sensor be the issue if it only hunts when started after it is at operating temp? Stop light idle is fine.