My ole 95 AC EXT was a batteried system. It started doing that, and the casue was the throttle position sensor connection. When it started that B.S., I just cleaned all the connectors and it always seemed to cure it.
If you can't find a loose connection, get a Tech Manual and start testing individual components. Most of the componets have ohm readings you can take to determine if there is a problem. On the Throttle Position Sensor, look through the entire range. There could be a bad spot on the thing causing you to test it through the entire range several times to find an intermittant problem. (It took AC two years to find this on one of my other ACs) Even I missed that one.
Just check all the sensors that are inputs to the Fuel Injection System. It takes time. But if there is a problem, you can find it, probably much quicker and cheaper than any dealer. Besides, once you learn this system and what to expect, you know right where to go to troubleshoot, even if there is a problem in the field.