My 1983 Chevy P/U is loosing power and slight missing under load starting about 40 mph. I have replaced all filters, fuels pump, fuel lines, carburator, cap, rotor, ignition module, coil, plugs, wires and even bypassed the gas tank with a temporary gas tank under the hood. There is a wire harness running from the transmission to the distributor, connecting into the ignition module. I’ve been told the distributor controls the locking converter on this model truck. Could the distributor be bad? Do I have problems with the transmission? converter. Truck runs great and shifts properly under easy conditions and under 35 mph.I put a new GM crate motor in this truck 2 years ago. Motor now has 19,000 miles on it. The truck has 93,000 miles on it.
Look at the EGR valve (sticking open) or perhaps a restricted exhaust…Does it have a “feedback” carb??