ok, my 5.9L seems to be running lean. it has no power and the ecm is spitting 02 sensor heating circuit codes. I am doing a "soft" restore on this truck . it has new exhaust with cat, new 02 sensors, new distributor ( cap,rotor,cam sensor,plugs,wires,coil). I cant find any vacuum leaks . The truck starts good and idles ok. also replaced plenum gasket and set up distributor timing

 

Distributor doesn't affect ignition timing. It DOES effect injector timing. You need to get fuel sync set. Need a scanner to do it.

 

Merged duplicate posts.

 

update: bad ground on o2 sensor heater circuit fixed my o2 heater circuit malfunction codes. now I have a tps code. voltage is good on the TPS through the range of motion however MAP voltage is all over the place. rechecked for vaccum leaks and found none. I'm going to replace both sensors . Update#2. Truck is fixed!!! replaced TPS and PMU isnt throwing any codes but truck was still running lumpy. Pulled plugs and found #1 and #3 not firing. I had 2 bad brand new Champion spark plugs!!! replaced them and now the venerable 360 runs smooth just like it should. Hope this post helps