Idle temporarily rises when A/C starts??

[Fluellen]

I've had the following "problem" for quite a while now. When the car is at idle, and the A/C cuts in or I turn it on via the snowflake button, the idle rpm go up by perhaps 100-200 rpm for a second or so, and then it goes down to normal.

My recollection is that it didn't use to do that... that the operation (A/C clutch engaged or not) was very transparent, almost unnoticeable.

Is my recollection correct, and if so, what could be the issue here? 2001 986S. A/C works fine apart from this...

Thanks in advance!

[thstone]

Generally, this is normal. The DME will slightly bump up the RPM when the a/c is on depending on several conditions. My car does the same, it won't bump up the RPM forever and then all of a sudden it will do it and I'm wondering what's wrong.

[stateofidleness]

Meh, seems normal to me. Mine does it also. On cold starts, it will do it's "normal" idle and then a few seconds in, the AC kicks in and the idle will bump a couple hundred rpm and then right back down to "normal".

[pk2]

Mine does the same. The A/C puts a quite a load on the engine and the throttle has to hunt around a bit to find equilibrium.

PK

[Fluellen]

Thanks everyone.

That's very odd. I could have sworn that when I first got the car - six years ago - it didn't do that.

In particular with the electronic throttle control, you'd think the system would be able to anticipate the load increase correctly and make the transition unnoticeable.