!990 C4 Cab very erratic running problem
 

I have a 1990 C4 Cab that is having problems. It will start then shut right off. If I start it and hold the throttle at 3000 rpm it will run but every 5 seconds or so it's like someone flips a switch and it drops a 1000 rpm and then comes right back to 3000 rpm. Seems electrical related because of the sharp drop it makes. Any ideas?

P.S. Drove the car yesterday and it ran fine but the day before it was at the body shop and they said it was acting up.

Do you have a chip installed? Stock clutch?

Clutch has been changed and it has no chip

I had a similar problem that turned out to be a bad cell in the battery. New battery solved the problem. If battery checks out okay, I would check all of the ground connections and ground wires, as well as both battery cables.