Hey. My car idles weird after i have driven it for a little bit and then i sit. It sounds fine then after a couple seconds it sounds almost like a misfire. It jumps down to 500 rpms or lower. I was thinking it might be from my exhaust but i dunno. I have an hks exhaust.

 

I just had the same problem with my 06. Took it to the dealer and and they replaced both cooling fans. Seems it was shutting off on overtemp. I guess it cuts fuel so it doesn't overheat and hut itself. Its still at the dealer waiting for a new top so I haven't driven it yet. I'm getting all the stuff done before the warranty expires in Feb.

 

Have you tried an ECU reset?

If you havnt got a scan gauge then manual reset is here

http://www.technosquareinc.com/350reset.htm

Any other mods like an air intake? Could be it wasnt reset after fitting?

 

My car has been doin about the same thing. its been idling high after i cleaned the throttle body out and now it idles about 1000rpms. also when i let off the gas and push the clutch in when coming to a stop the rpms will drop down to about 900 and then jump back to 1500rpms and stay there for about 10 seconds or so and then slowly drop to 1000 and sometimes drop down to 900 and stay there. Also when i start it up and i will let it run for a few min. sometimes it sounds like its misfiring and motors shaking around, today it did it and thru codes for 02 sensors 1 on banks 1 and 2 saying its running rich but thats the only codes. Also i drove it about 20min. and parked it for about an hour, came out started it and all seemed fine. Drove for about to min. and it started acting like it was misfiring again when i stopped at a light. I reved it up a few times and it went away.

I just put new plugs in a week ago, tested the coil packs all read fine. It has been cold lately but its not doing it every day.