hi, people i m having a funny problem in my car when on idle the rpm jumps a little and even the daeler failed to get to the cause they charged me almost 400 dollars they said it was the supressor switch that they changed 2 of them and they said they changed the spark plugs too but even after that the problem is still there any idea would might help me a bit i have a 1993 400e with 35,000 miles
thanks
mani