I recently did the timing belt on my 2008 LS sedan. While I was at it, and since the airbox was out, I cleaned the throttle body (not by removing it, but just by opening the butterfly valve, spraying the cleaner in there and wiping with a lint free rag). I did the idle learn procedure after getting everything back together.
Before the timing job, when starting the car it would idle up to about 1200 RPM for 2-3 seconds and then come down to normal idle (750 RPM). For the first week after working the timing belt, this was still the case.
About a week ago however, whenever I start the car (cold or hot), the idle surges up to ~2000 RPM for 10-15 seconds and then comes back down to 750 RPM. If I tap the gas or pump the clutch and shift through the gears it seems to bring it down quicker.
I would think this can't be good (at least when the engine is cold) since the oil is cold and more viscous, and not lubricating the piston rings/cylinders all that much while at this high idle.
Anyone have any ideas on this one?