My 1990 accord EX has a rough idle when in gear at a stop, it is an automatic. I especially notice that the car idles very rough as its warming up in the morning. Once the car has reached full operating temperature it smooths out however, if I run the AC with the car in gear it will idle rough again. The RPMs don't drop below 800 even with the AC on so I don't think its an issue with the engine idling too low. It seems to be a tuning issue. Any ideas on what I can do to troubleshoot this?

 

I suggest just doing the regular maintenance stuff, like check the air filter, check the plugs, other stuff, i dont think that the rough idle is due to anything major. I think you may benefit from trying out a fuel system cleaner.

 

Good point on the fuel system cleaner, I can give that a shot. I have done the general tune up stuff (plugs/cap/rotor). I recently had the timing belt and water pump replaced. I have a CAI and a new filter (its my daily driver so it remains completely stock otherwise).