Expert: Sean Halliday - 7/25/2007

Question
QUESTION: I have a 98 Mitsubishi Eclipse 5 speed transmission. I have been having a problem with my engine reving up & down between 500 & 1500 when the AC & Fan are on when the car is idling. It just races up & down constantly. I just had the car tuned-up, all new belts, new water pump & the idle arm cleaned. Any ideas?

ANSWER: Sounds like your idle control valve or the throttle sensor.You will not be able to test these your self as its a job for a tech or shop unfortunately.As they are expensive ,its better getting the right part than guessing.

---------- FOLLOW-UP ----------

QUESTION: What is an Idel Arm, the mechanic I had tune up my care said it might be that.
Thanks

Answer
The arm is on the throttle body which connects to the accelerator linkage.There are 2 sensors on your throttle body,one will make the car stutter on take off and the other will make the idle run high,the second one is more likely the problem on the mitsubishi..it is this one which is connected to the idle arm.