I have a '97 Protege, 164K miles. Runs fine but won't idle with the AC on. Idles OK when off around 750 rpm. With AC on it barely holds 250. Thought it might be the Idle Air Control Valve but don't understand when only with AC on.

Suggestions?

Thanks
Ben

 

Time for a tune up.

 

The extra load of the compressor will reduce the rpms. The ECU is suppose to command the IAC to raise the idle.

As the Reaper said, start with a good tuneup and clean the IAC and passages.

I'm assuming there's no check engine light.