87 Chevy Pickup Timing Problem
Have 87 Chevy full size pickup 3/4 ton 4wd 350 TBI - engine and truck are all stock. Truck has erratic idle. I have tried to set timing but when I try to put in bypass mode the truck shuts off and will not start at all. When engine is running and have pulled the bypass connector the truck shuts off immediately. Truck is showing a code 42 - have installed rebuilt dist with new ignition module/est. Have replaced ECM (did not replace PROM). Installed new external coil, new O2 sensor. I replaced the IAC valve thinking it would solve the idle problem but it did not. Service manual said wires from dist to ECM has open circuit - but checked continuity on all four wires and there is no open circuit. Truck does have slight hesitation from idle and very slight bit of surge at speed over 45. When truck is cold it is very cold natured. The only way I can get it to run somewhat ok is by setting timing at 22 degrees, but it still dies no matter where it is set when I pull the bypass connector.