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jingai · Joined: 21 Oct 2002 Posts: 11 Location: Melbourne

I've only noticed this twice so far, but I figured I'd toss the question out there..

Two times after I just purchased the car it would idle "rough" at stop lights and seem to lose power (RPMs dropped roughly 250 or so).

I honestly can't remember if I had the A/C on, so that may have been it.. and in fact, I haven't had the A/C on once since it quit raining on me daily, so it may have just been that. It just seemed like a pretty significant drop, so I want to know if it's something I should be worried about or not.

edjack · Joined: 04 Feb 2002 Posts: 3887 Location: San Jose, CA

How many kms on the car? Has the fuel filter ever been changed? Did the Check Engine light come on?

jingai · Joined: 21 Oct 2002 Posts: 11 Location: Melbourne

Only 12,800 miles (20,600 km) on the engine. I just bought the car, so I don't know when the filter was last changed. I am getting the dealer to do oil/filter change, coolant flush, and spark plugs on thursday, though.

jingai · Joined: 21 Oct 2002 Posts: 11 Location: Melbourne

Oh, and the CEL never came on. I currently have three yellow lights on the service panel as well.

DaveB · Posted: Thu Oct 24, 2002 12:28 pm Post subject: Rough idle and power loss

What engine do you have? M44 or something bigger? The A/C shouldn't make any difference at all to the idle speed. The DME senses it and gives it a bit more gas to compensate. That's how mine works. the only time I notice a dip in idle speed (750 - 700ish) is when I close the door and the windows lifts up, the DME can't compensate for that.

jingai · Joined: 21 Oct 2002 Posts: 11 Location: Melbourne

quote:
Originally posted by DaveB:
What engine do you have? M44 or something bigger? The A/C shouldn't make any difference at all to the idle speed. The DME senses it and gives it a bit more gas to compensate.

Eh, no it's just a wee 1.9 liter 4 cylinder. In some cars with 4 cylinder engines I've noticed the A/C does cause a dip in performance, but after trying it off and on in the Z3, you're right, it doesn't appear to.

And FWIW, it hasn't happened again since. Maybe it had something to do with the fact the car has very low mileage and is 6 years old, so it probably just needed some exercise.

DaveB · Posted: Sat Jan 04, 2003 7:32 am Post subject: Rough idle and power loss

The 1.9l 4-cyl IS the M44.

87325e · Joined: 10 Nov 2002 Posts: 90 Location: Winnipeg, Canada

I had problems with my Air flow sensor. The car would rough idle, then sometimes it would just die. It would seemto surge also. If it is your air flow sensor, it is easy to fix.

The Puffin · Joined: 14 Apr 2006 Posts: 3 Location: Borlänge, Sweden

A common cause to sudden drop of RPM during idle is a faulty temperature sensor in the intake airflow. The drop in RMP sometimes is so large that the engine will stall.

Once the engine is up to temperature this wont happen during idle.

/Sven