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Question I have a 1992 Mitsubishi Galant, 2.0 liter, SOHC engine with 5 speed manual transmission. Car does not idle well when engine is warm and the air conditioner is on. If AC off engine idles just fine. Performance is good at any speed above idle with AC on or off. With a warm engine, AC on, the RPMs drop to the point that AC compressor disengages, Then RPMs increase and compressor engages again and RPMs decrease. Cycle continues while the AC is on and often the engine stalls during the process. Turn off the AC and car idles well. Engine RPM does not increase when the AC is turned on. Is there a relay or other device that has gone bad? Thanks, Mark

Reply The idles speed control circuit of your Mitsubishi is designed to raise idle RPM to compensate for the load of the a/c compressor. This is obviously not happening. You may want to check something as simple as the condition of the throttle bore for cleanliness. Any more involved tests would require a digital volt ohm meter or a scan tool for accurate diagnosis. Angelo Silverado Auto Service