I've replaced the spark plugs, wires, distributor cap, rotor. Shop replaced timing belt and water pump. Today, the catalytic converter was replaced (P00420 was being displayed). Car still idles very rough. I know that whatever the root problem is probably took the cat. converter out and want to fix before it trashes the new one. Shop looked for problem and could not find anything wrong. Car seems to run fine when driving and if I shift into neutral, idle drops and it isn't so rough.
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1997 Kia Sephia Question: Idles rough in gear
Answer #1overbys from Overbys Inc, February 25, 2011, 08:12Master
check the motor mounts before you replace anything else.
Replyeriggins, March 07, 2011, 09:14Rookie
Sure enough, a motor mount was busted. The check engine had been coming on every 30 miles with a P0300 (random/multiple misfire) and hasn't come on now in over 300 miles and idles much smoother...its like having a whole new car. Thank you very much.