Cold Idle Question
 

My '09 C2S used to idle high (~1,100 RPM) on a cold start, then settle down to about 740-750 after about 20-30 seconds. Recently, it stopped doing that. On a cold start, the idle speed is 750. No more high idle. This behavior started shortly after 60k service. Is this something that needs checking out?

The only other thing that's different is that the car stalled on me once. I didn't think you could stall a PDK. It started right up and hasn't repeated this behavior (yet).

Yes, have it checked out. That is not the normal behavior.

My WAG is there is a coolant or possibly an intake air temperature sensor problem and as a result is supplying a higher than actual temperature.

It could be coincidence but it could have arisen from the service. A sensor connection or wire got harmed during the service.

I have 66K+ mile on my '08 C2S. More recently my idle had been lower and rougher than normal/typical. The Durametric would intermittently catch an issue with my O2 sensors. After failing an emission test this year I took it to the p-dealer as the car was still under CPO. Dealer found the same issue... they called it a "sleepy O/2 sensor" issue = sensors are borderline. FYI, O2 sensors are not covered by CPO. Not a big deal as it only takes 30mins to R&R the 4 sensors. After swapping the sensors out my car passed emissions testing here in TX and idle is back to normal. If you don't DIY just have the p-dealer connect your car to the PIWIS but if the sensors are "sleepy" it may take a few trips to the dealer to catch it in that state. My sensors were borderline enough that it would not throw a CEL. I waited until the Durametric caught my sensor in it's weakened state and then drove it immediately down to the p-dealer to show them. Wish I had known upfront that O2's were not covered... I would have skipped dealing with the p-dealer all together. GL.

It is normal (normal to my car at least) if the outside temp is still hot as well as the engine or coolant temp. I've noticed that on summer, even if the car sat overnight in our garage (which stays very hot at night), it will start without the higher idle setting. Let it cool really well for a couple of days if still hot outside or in your garage, and see if this low initial idle reoccurs.

Thanks, all. I also noticed that the engine bay cooling fan is running more frequently than normal (which is hardly ever). Having it checked out next week and will report back.

My '09 C2 (36,700 miles on the odometer) has also started to skip the 20-30 second high idle on cold startup about 3 weeks ago, no real change in weather here. Also the engine bay fan has stopped cycling on when parked in the garage with a hot engine. Normally, the fan would kick on for 15 or more minutes on a hot day after parking with a hot engine. Something has changed, no CEL or other alerts from the car.
Last service in May…oil change, plugs, filters, brake fluid flush and installed FD Motorsports exhaust.
I am thinking there is a temperature sensor messed up. I have an appointment at the dealer and will report back with what they find.

My 2009 too. Must be contagious.

I have a 2009 C2S as well with 28500 on the clock. Mine also started doing this within the past few months although it is sporadic at best. What I have noticed is if my car sits for several days it always idles at the 1100 RPM mark and after about 30 seconds drops to 700 - 800 RPM with a smooth idle. If I drive it on consecutive days it is hit and miss. I live in Atlanta where the temperatures are still warm (80+) and humid. Not sure that matters. Also, I just had my car in for its annual service and there was nothing to report that would be causing this issue. I would say it is not a concern, however, for peace of mid have it looked over if you would feel better.

Maybe Porsche has issued an OTA (over the air) software update for all 2009 Carreras) like cellphone providers do for smartphone operating systems :-) Obviously, I'm kidding, but it's weird this has started happening to you guys all around the same time.

Sorry I can't be helpful, but maybe at least funny. Good luck finding the fix.

Picked my car up yesterday from the dealer and here is what they found:

- the engine bay fan had failed and it was replaced.

- no faults or codes relating to the cold start idle behavior and they said it was working as designed