Question
eclipse
i have a 93 eclipse 2.0 Non turbo with a 5 speed. My car runs like a top when its cold. but when it reaches operating temp it starts to idle like crap, hesitate or stumble from a stop or while just cruising in a low gear like 4th with just enough pressure on the gas to maintain speed. while accelerating or WOT or driving down the highway it runs great. the symptoms seem to show up only at lower speeds. and i have replaced feul pump/filter, plugs, wires, ignition coils, mas air flow sensor, throttle positioning sensor, air filter, and egr valve. still no difference. im usually a damn good do it yourselfer but this has me absolutely stumped any advice you can offer would be much appreciated.
AnswerNick,
One of the components that is bypassed by the car's computer prior to the engine reaching operating temperature is the idle speed controller (ISC) or sometimes referred to as the idle air controller (IAC). It's a stepper motor that regulates the flow of of air when the throttle plate is closed. The throttle body has a component within it called the base idle set screw (BISS). Over time, the small o-ring on this small plastic screw develops leaks, and the idle becomes unstable.
Any fault in the charging system can also be suspected in idle problems. Have your alternator and battery checked to make sure they are performing nominally.
If all else fails, have your car's computer checked out. You can read this article for more information.
http://www.90gsx.com/eclipse/cap/caps.htm
If your ECU is damaged, the first signs of this are poor starting and idling.
Good luck!
Anthony
