No, idling is unlikely to change immediately by unplugging the ISC since it's just a valve. Unplugging it won't cause the valve to suddenly move (quite the opposite) so no change to the idle speed would be expected. However it should change when switching AC on or off to counter the extra load BUT ONLY if the throttle closed switch has told the ECU the engine is idling. If not, the ECU is trying to run the engine based on sensor readings (MAF etc.) and the ISC isn't in the loop at all. You will need to fix/verify the TPS before you can know whether the ISC is working or not.


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