rough idling on 2002 Mitsubishi Eclipse

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Whenever my car is in idle position (car not moving but engine is still running) my engine has a rough roar and is vibrating a lot until I put in neutral. (It also seems to almost stall and die but regains engine idling) What could be the possible cause for this?
(1) Answer
A dirty throttle body can cause rough idle @ cold start ups, and cause sluggish performance, it will cause the computer to over compensate gas to the engine causing, sometimes a little smoking at the tail pipe. only use THROTTLE BODYspray cleaner .With the car off, remove the plastic air duct to the throttle body and open the throttle manually wide open by hand. then spray into the throttle body to remove the gummy residue as far back as you can see. then start the car,it may need reving up some to clear out the cleaner in it, then hold throttle barely open and spray cleaner into the throttle body, using short burst , be careful to not over rev engine, rev enough for it to clear out the sprayed cleaner. stop engine and reassemble ducting. I have found this to improve idle, (reduce raw gas smoke) and improve performance. you should use a good gas tmeatment additive every4 or 5 tanks of gas to help it from getting that bad again.