[JL8Jeff]

The air pump might share a circuit with something else and therefore shut down something else when it acts up. Did you have it scanned for any other hidden codes? Do you hear the air pump turn on when you first start the car? If not, it might be siezed up and putting a load on the system. If you don't hear it, try disconnecting the wiring to it. It might trigger a code but the car should run like normal. On my old 93, one of the AIR check valves went bad and let hot exhaust go back into the AIR lines and in winter that allowed condensation to build up. It eventually filled the AIR pump with water and froze solid one morning and took out the fuse. Did you also check the battery to make sure the terminals weren't about to rot out? The AC Delco batteries are known for the terminals rotting from the inside out and will eventually break off.