Just after warm up when i raise the rpms to around 2000 they drop to 1500 then go back up to 2000 and stays but doesn't have to be 2000 could be 1500 then drops to 1000 then back up to 1500. This all happens pretty quickly and after full warmup it doesn't do it anymore. I don't really know why it would do that...i don't think it is ecu because i have reset that...and the iac should probably give me a check engine light...but havn't got one of those. Another thing i have noticed is that when it first starts up until warm up there isn't much exhaust comming out ... after warmup it gives more exhaust flow(basically normal)...really bizzare because or cource after warmup it is at lower rpm's!

Thanks

 

my car sometimes does that as well...........i'm not too worried about it though.

 

my car does it too , but at higher rpms when its cold , like almost 3 k for the first min or 2 , after that it goes down to 1.5k then down to norm . . .

 

I just recently had this same problem where my car went from 1k rpms to 3k and back down. even when it was warm at like stop lights. most annoying thing ever. I am 98% sure its your fast idle valve on the throttle body. There is two so you gotta check both of them to see which one has gone bad. Dont go out and buy one from the dealer, because its a dealer item. They will rip u off. You can either get one from a junkyard or rebuild the one u got. I rebuilt mine myself. The first one is right behind the throttle body/intake manifold. its about 2-3 inches in lenght. black and silver. near the firewall. the 2nd one is in front of the intake manifold under the throttle body. take those out and make sure there is coolant flowing through the hose and valve.