The Causes of an Idle Surge
The Causes of an Idle Surge Fluctuations in engine idle speed can be annoying and may even cause stalling at idle. Engine stalling can be dangerous, because power assistance is lost to the steering and brakes. Idle speeds below those specified by the manufacturer will affect the performance of the power steering pump, alternator and AC compressor. Emission control devices also require a minimum engine speed for effective operation. Surges that accelerate engine speed could cause unexpected vehicle movement. Air Supply A clogged or obstructed air filter can cause surging at idle, and foreign objects can enter the filter housing at any time. Any debris in the filter or housing might restrict air flow to the engine enough to affect idle speeds. Clean the throttle body or carburetor venturi(s) after replacing a severely dirty air filter. Aerosol products designed for this purpose are available at any auto parts store. Instructions for use are on printed on the can. Fuel Sup...