I have a 95 GMC Jimmy with the 4.3 and it has a missfire upon acceleration. I changed all the plugs and wires and the distributor cap along with the throttle positioning sensor and it still continues to missfire. Cant have the computer read because the guy before me did something to wiring under the dash. Help please???

 

What brand did you use for the tune up? These trucks like ac delco only! Did you replace the rotor? Have you tried to clean the MAF sensor and EGR valve?

 

Do the 95 4.3 have spider injector assmbly? My 99 4.3 got a misfire from a pinched wire on my aftermarket spider assmbly. It was flooding a cylinder with fuel from a constantly pulsing injector.