98 blazer 4.3 Vortec. I have had problems with the engine idleing since i got it a year ago. The other day I changed the thermostat. and when I was filling it back up I noticed my A/C pump would kick on, run for about 20 seconds and then shut off, so on and so forth, with the switch turned off. I guess it has been doing it the whole time I have owned it. So I just unpluged it now my engine idles fine. It would cut out on me like when i stoped at a stop light or parked and left it running. Wanted to know if anyone else has had this problem, or if it is suppost to do that. my pump seems fine and gets really cold, could it be in the wiring or the switch?

 

If you have it in defrost that's normal. Even though it's 10 degrees out mine cycles briefly, it dehumidifies the air a bit.

 

Will it hurt it to just leave it unpluged? Cause if so I will just hook the pump up to a switch. I get better gas mileage with it off all the time.

 

The clutch on the compressor periodically engages to relubricate the system. If left disconnected for long periods of time, you can develop leaks in the system that will be expensive to repair later on.

Your clutch is cycling because the system is already low on pressure. A quick recharge using one of the kits available at most autoparts stores and some retail shopping centers should bring your system back up to proper pressure.

Your truck should not stall regardless of the A/C status. This indicates that you have problems elsewhere. Most likely, the IAC (idle air control) valve is at fault. Most likely, a quick cleaning will remedy the situation. The IAC valve can be removed and reinstalled without replacing its sealing o-ring if done properly.

While you are cleaning things, it wouldn't hurt to remove the EGR valve and clean that as well. Before you start, get a new gasket, improved (gasket with the screen in it) for the EGR valve.