I have a 01 Sub with 125,000 mi. Has original plugs/wires, change oil when light comes on and use Mobil 1 syn 5w/30, change trans fluid between 30-40,000 mi. Probably needs new fuel filter, had fuel pump changed with wiring harness recall. Recently changed the belts. Lately when the AC is on (cold now but still does it) and at a stop light or idle the RPM's and engine surges down - almost like it is going to stall but never does. Then when accelerating it ever so slightly stumbles and then drives fine until the next stop. If I turn off the AC then it runs fine. Suggestions - alternator, plugs/wires? I am a DIY so let me know what you think. Thanks, Nelson

 

Clean throttle body and clean or replace IAC (idle air control). The IAC is used to keep the idle up as the load is increased.

 

Thanks! nls

 

Sounds like compressor is starting to go (locking/dragging). Did you change the belts b/c they had to remove the main belt to replace the broken A/C belt?

 

I finally got around to cleaning the IAC, but there isn't one on a 2001. So I removed the throttle body and cleaned it. While driving yesterday, turned on the AC and it was down surging again. Any ideas for what else could be causing this? Thanks, Nelson