I have a 2008 Lancer GTS with Nav. Whenever I turn the A/C on and I'm in drive (let's say at a stop light) I can hear the clutch to the A/C constantly(like every 2 seconds) engaging and disengaging. When it does that my rpm fluctuates heavily from 250-750rpm and sometimes even shuts off the engine. This doesn't seem to happen while driving expressway. What could be my possible problem?

 

possible throttle sticking? How many miles on it? Any check engine light or other warnings?

 

I have 108000. I was getting PO750 for a while but that seems to have cleared itself and also not related to the problem. Not sure about throttle sticking as this only happens when the a/c is on. No other warnings happening

 

Check the coolant temp sensor

14 − 17 kΩ [at -20°C (-4°F)]
5.1 − 6.5 kΩ [at 0°C (32°F)]
2.1 − 2.7 kΩ [at 20°C (68°F)]
0.9 − 1.3 kΩ [at 40°C (104°F)
0.48 − 0.68 kΩ [at 60°C (140°F)]
0.26 − 0.36 kΩ [at 80°C (176°F)]

 

Also, you have an old thread concerning this issue. You should continue on with that rather than start a new one.