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Slightly Low Idle

OK, so my 2000 S is near perfect. Near.

She runs beautifully at 53k, except for one thing: slightly low idle. I realize the tach is probably not the best way to determine this, but that is what I am going on, please do not whip too hard :(

She starts wonderfully and runs wonderfully. But once warmed up, she drops to about 625. She still runs great, but it does make the car feel like it is idling too low. No real hunting goes on, maybe a little bounce between 625 and 650, but is extremely slight, and only sometimes. The A/C on brings the idle up a bit, but I think only to about 700-750. It still runs fine there too, but just a bit too low. Absolutely now stumbling experienced wither way.

I have searched the forum and two things seem to be possible: AOS or ECM reset/relearn.

For the AOS possibility- I have no issues with excessive pressure with the oil cap. I also have no smoke at any time. I am thinking next thing to check is for oil in the tube or TB. Any other advice on looking for a failed AOS in the very early stages?

For the ECM reset - I have complete records from the PO and the MAF was changed recently. I am not sure if anything in the intake was cleaned and it seems this could be why the relearn might help. Am I completely off on this? If I do try the reset, how long do I need to disconnect the battery for? Also, how many miles of driving does it usually take to relearn typically? Lastly, any advice on driving style to take during this relearn phase?

Thanks guys!!! I have read through quite a bit on this forum and it is by far the best forum for Boxster info/advice. And besides, Jake Raby visits and posts regularly, who could ask for more?

Quote:

Originally Posted by Ebell914 (Post 384315)

If I do try the reset, how long do I need to disconnect the battery for?

A few minutes will do the job fine. Don't be surprised if the engine runs rough at first startup.

Quote:

Originally Posted by Ebell914 (Post 384315)

Also, how many miles of driving does it usually take to relearn typically?

30-50 miles.

Quote:

Originally Posted by Ebell914 (Post 384315)

Lastly, any advice on driving style to take during this relearn phase?

Varied driving. Be sure to do a couple of cold starts and a few hot starts. Be sure to drive between 30 and 50 mph and at highway speeds. Then do around town stuff.

Also try to run the engine with the MAF sensor disconnected.
If replaced recently, it might be the wrong part (I think there are 3 or 4 different MAF part numbers) or an aftermarket part no doing its job.
If the MAF sensor is at foalt, the engine should idle better when disconnected.

Reset the ECM. It went almost immediately back to low idle. I guess it is time to mess with the MAF. :(