First let me say I have been in the business for 17 years as a GM tech... Buick & Cadillac. I left in 2000. Now that I pumped up my ego here's what deflated that ego: I have a 1992 Silverado pick up with a 4.3 and a five speed. This truck is cherry. One problem that I cannot diagnose and I've even taken it to a friends shop and dropped 1K and drove out with no answer. When I drive this truck there is absolutely no power. Can't get out of its own way. If I disconnect the field wire to the alternator, she drives like a raped ape ... When I reconnect the field no power and I notice the spray pattern on one injector doesn't quite look right and only kind of half sprays starving one bank when the field wire is connected but this problem goes away as soon as I disconnect the field. Here's what was done: Swapped ECM, replaced distributor, replaced MAP & TPS, compression test, timing is set proper, no vacuum leaks, new IAC.... Also replaced both injectors ... I have never seen this happen and was wondering if anyone has seen this or if anyone has any ideas because I'm fresh out of ideas and I'm ready to sell this for parts. Thanks!

 

Have you tested or replaced the alternator? Is the field wire in good condition with no insulation missing?