Questions and Answers

GMC Jimmy Runs Bad Q. I have a 1989 GMC Jimmy with a 1992 V-6 Vortec engine. The engine runs fine if its allowed to sit a couple of days. If ran frequently it jerks and acts as if its not getting fuel. Someone suggested checking the Oxygen Sensor. I took it out and heated it on the bench with a propane torch.

It ran up to about 0.9 volts and then quickly dropped to 0 volts with the torch removed. This is supposed to be okay. The sensor did have some black carbon like build up on the sensing tip as if the engine had been running rich. Any suggestions as to where to go next?

A. To me this sounds more like a basic ignition problem or lack of fuel. Maybe an injector not spraying correct? It's very unlikely that a sensor is causing this. Try looking at the injector spray pattern when it acts up. Also, try spraying some water onto the distributor cap and coil and see if it starts running bad.