1995 Chevy Cavalier idle air control valve

If you have faulty IAC your motor will idle badly. The revs will not stay at a constant level, even when your engine has reached operating temperature. If this is the case then of course the fuel mileage will be horrible as well. However, a faulty PCV valve will cause poor fuel mileage without bad idle. A stuck-open PCV valve will allow unmetered vacuum to cause a lean air/fuel mixture. The engine management system will "fatten-up" the fuel injection spray time (volume of fuel) to compensate for a lean air/fuel ration, thus using more fuel to accomplish the same task.


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