350 motor was running rough at low speed and hard starting. runs great with mapp unplugged so i put in a new mapp, nsame cthing runs terrible when the mapp is plugged in and great when its unplugged?
You are describing a condition that should make the vehicle run worse...(unplugged, all out rich)...so look to fuel problems, such as pump, pressure, etc. anything that would make it too lean all the time. Good Luck ATM
Search Chevrolet Chevy Van Questions
Chevrolet Chevy Van Experts