Hesitation, Cleaned MAF, No More Hesitation But Now Rough Idling?

[panameras]

Boxster S MY00, 48k Mi. Had hesitation below 2000rpm on all gears, cleaned MAF following mikefocke's page, hesitation seem to have gone away but car now idles funny. Keeps dipping from 900rpm (or whatever the standard idle should be) to around 500rpm, even down to 200rpm occasionally. And sometimes it also holds at 900rpm for up to 5 seconds at a time.

Car had a similar rough idle problem less than 10k Mi ago, the stealership replaced the 2 cam tensioners and cost me a forture. So I don't think it would be the cam tensioners again this time, but the symptoms are alarmingly similar.

Appreciate any help.

[Loren]

The MAF has little to nothing to do with idle - it measures air flow as you open the throttle.

You likely need to clean the throttle body. Do a search here as this has been covered many times.

[panameras]

Thanks I've already read the throttle body DIY. But what I don't understand is why would I get rough idle now after cleaning the MAF as it was fine before when the car was having hesitation?

Do I need to reset the ECU (unplug battery?) at all after cleaned the MAF? There was no CEL by the way.

Edited May 9, 2009 by panameras

[Rising_Sun]

Sounds similar to my problem after I cleaned the MAF on my 01 S I got slightly rough idling and then shortly after a CEL, I was cleaning for preventative maintenance but obviously this backfired on me!

To resolve the issue I cleaned the MAF again, made sure it was dry and then reset the ECU (disconnect battery). After a test drive all was well again, smooth idling and no CEL. That was 1000m ago and all is well. I don't know how the idling can be upset but maybe as a sympton of the MAF suddenly delivering different data is enough to throw the system, hence requiring the ECU to learn the new settings.

Another conclusion I made is - if it aint broke then don't fix it!

[panameras]

Thanks. That could be it, but if the MAF wasn't dry yesterday after I cleaned it, it surely should be dry now. How long did you leave the battery disconnect in order to reset the ECU?

[geoff]

Thanks I've already read the throttle body DIY. But what I don't understand is why would I get rough idle now after cleaning the MAF as it was fine before when the car was having hesitation?

Do I need to reset the ECU (unplug battery?) at all after cleaned the MAF? There was no CEL by the way.

A few weeks ago I commented here there seems (to me, at least) to be an unscientific correlation between cleaning/replacing MAF and rough idle afterwards. If you do clean the throttle body and that solves the problem, please let us know

I think you should only need to unplug the battery to reset the ECU if you swap in a new MAF, but it couldn't hurt anything to try it anyway

[panameras]

A few weeks ago I commented here there seems (to me, at least) to be an unscientific correlation between cleaning/replacing MAF and rough idle afterwards. If you do clean the throttle body and that solves the problem, please let us know

I think you should only need to unplug the battery to reset the ECU if you swap in a new MAF, but it couldn't hurt anything to try it anyway

Strangely enough, this morning when I started the car the idle has fixed itself! :thumbup: It ran above 1k rpm for 10 to 15 seconds or so (not sure what it was but happens all the time when cold start. Fuel pump?) then settled down to just below the 800 rpm mark and stayed there. What a pleasant surprise! I was prepared to spend the night doing the throttle body cleaning after work.

I think the "unscientific correlation between cleaning/replacing MAF and rough idle afterwards" might have something to do with an un-dry MAF. The rough idle happened right after the MAF cleaning and was still happening two hours later when I took the car for a drive. Although I did let the MAF dry for an hour in the air before reinstalling, it may have not been completely dry. Now after spending more than 24 hours sitting in the garage, the rough idle has gone away.

Then again, it could be just the ECU needed time to adjust to the "new" cleaner MAF. Whatever the cause I'm just happy that its solved. :cheers: