I have a 1990 Camry. The idle is very rough during warming up. Engine speed would suddenly increase to very high for a few seconds and drop back to near stall. It will repeat this before it's completely warned up (20-30 minutes of driving in cold days). The engine will stall if this (surge and drop) happens during acceleration. It only happens during warming up. It does not happen if the engine is completely cold (first couple of minutes of cold start) or completely warmed up (hot).
Does any one have any suggestions where I should start?
Thanks for any help!
Have a nice holiday!