idle surges in cold weather

[bbensten]

My 2001 325i idle surges first thing in the morning on cold days. Any idea what is going on? After driving a few miles thing return to normal

 

[eddo1]

What do you mean by surges? I know that my rpm can flucutate up and down (between 400-1400) more in cold weather and in traffic. There was a problems with the VANOS unit. Dealer said there is a screw in the VANOS units that goes in and out that regulates the rpm. The screw they said is the first thing that gets worn. Replacing it didn't completely fix the problem but is much better. Now that my warranty is out I guess I have to live with it. Maybe I'll sell the car in the summer!

 

[MrElussive]

The car follows a warmup process (pre-programmed). When you first start up on a cold start, it will rev to and idle at about 1,400rpm. The car does this as a warmup procedure and once the engine starts to get warm, it returns to normal.

 

[dcaron9999]

cold idle fluctuations

I have a 1999 328i with the same issue. When the engine is in the blue temp gauge zone, the RPM drops to 500 and bumps back up to normal, when sitting at idle. Had the dealer check for this a while back, the replaced the "main relay" and reprogrammed DME with a new version... ????

The problem still exists, but is not terribly annoying, as it goes away as soon as engine warms up a bit more.

 

[selavia]

My buddy told me that his 2004 Mach I does that and he took it to the dealer, and they told him that when it dips like that, the ECU is just checking the MAP Sensor. This makes no sense to me, but does this sound like it could be the solution? Also my car did that (but then the check engine light went on and it twas followed by a series of unpleasant events) and the problem was a cut / tear / stabbing of my air flow mass meter boot.

Sean