I have a 2000 Silverado with the 5.3. Recently after changing out some o rings for the ac system and filling it back up I've had a weird issue pop up (not sure if its a coincidence or not). When driving from about 10-30 mph it'll do this thing where the temperature gauge drops and the truck will almost stall (or sometimes actually stall) i can have the petal to the floor and it does not even rev when doing this. I can let my foot off the gas and let it coast for a few seconds it stops, i did replace the spark plugs and wires a few months ago and it has a new fuel pump.It does not drop fuel pressure when this happens. Any suggestions on what to check? The check engine light turns on every so often with a P0332 knock sensor circuit low input code and i don't think its a fuel issue so im a little stuck, thanks.

 

Go back over your AC work and make sure all the electrical connectors you might have disturbed are seated properly.

Good Luck!