Same problem here - going on two weeks old.

 

i know what you are talking about. i have been wondering the same thing too. i figured that it had something to do with the added load of the cooling fan kicking on.

 

do you drive w/ the AC on? b/c my friend had the same problem with their neon...

 

To answer the last question, no i dont usually drive with the a/c on.

Went to the dealership and explained what i was noticing and asked if it was normal for the car to do that. They didnt really answer, but said they would take a look at it. Well they said they checked it, to what extent im not sure, the receipt says npf no problem found. They were pretty busy so no one really had anytime to chat about it...oh well. I figure i got 3 years for something to go wrong or get worse if it is a problem.

 

I know what you mean. I believe it has something to do with the ECU and the throttle-by-wire. In a normal car, when you take you foot completely off the gas pedal, the throttle closes. In the tC, when you take you foot completely off the gas pedal, the ECU decides whether to keep it open a little and slowly close it over some period of time, or close it completely (which I think it rarely does.) Some other people have described it as feeling like driveline lash when you're trying to go a constant speed in a lower gear, and that's pretty accurate. Honestly, if there was an ECU program that would give me control over the throttle, I would switch it on. In some cases maybe the ECU is smarter than I am when it comes to modulating the throttle, but most of the time I just want it to do what I want.

 

Mine seems to be idling a bit low. It stays around 700 a lot of the time and vibrates a little bit. I haven't noticed yet if that is only when the engine is not warmed up.

 

That sounds pretty normal. I notice mine vibrates just a tiny bit at idle, which is usually around 700 rpm.

 

I just noticed this on mine as well. Did anyone ever get a definitive answer about what causes it?