Mitsubishi Repair: 1995 Mitsubishi Mirage, throttle position sensor, 1995 mitsubishi mirage

Question
The idle was fluctuating at times from 1,000 to 1,500 rpm's rapidly.  we could shut the engine off, restart it and all was ok.  It would sometimes be days before it would happen again.  NOW!  it does it every time and restarting does not help.  I have been told it may be O2 sensors.  Tip! The engine service light does "NOT COME ON".  So I guess it's not emissions.  Can you help?
Thanks,
LB

Answer
Lanny,
Fluctuating idle speeds are usually caused by an air intake component.  Check for air leaks around the air filter housing, and all the way back to your intake manifold.  If you've recently had your air filter replaced, there may be a leak allowing unmeasured air to enter.  Have your Idle Speed Controller (ISC) checked to be sure it's functioning properly.  That is located on your throttle body. It is used to regulate your idle speed.  When it malfunctions, it'll bounce your idle up and down.  Other items to have checked are your throttle body, throttle position sensor, and ignition timing.
Good luck!