i have a high idle problem and a vibration when i first started trying to pin point the problem took it to mechanic got and error code of cylinder 4 misfire so i changed the spark plugs, wires, ( 2 times) checked compression and changed the fuel injector, o2 sensor, gas pump, timing belt water pump, before reseting the computer, now check engine light is on, still a rough idle and vibration i want to say only when cold but it just depends it might go away for a sec when i shift it in drive and then ill put it in park and ill idle at 2 or 3000 and attempt to go down.99000 miles
Mitsubishi galant 2000

 

well dude, if all the work you did was done correctly, sounds like you got a internal engine problem. i had one like that a few years ago, same issues but p0302 v6 model. turns out the the rod was bent on #2 cylinder. engine sucked up some water durring a bad rain storm. customer neglected to tell us that info untill a few days later. he traded the vehicle in, and the vehicle got wholesaled. felt sorry for whoever bought it!!

 

Check the O2 sensors