Just bought a 97 gmc sierra with a 5.7 Vortec. Before I bought it the dealer acknowledged it had a problem before they'd deliver it, he said the number 3 cylinder wasn't getting enough fuel. He assured me it was fixed and I met them half way to pick it up and once I hit the interstate the service light came on solid. The pickup still drove well at 70 mph, didn't get hot, didn't feel any bucking or anything. When I got off the interstate and came to my first stop the service light started flashing. It has minor vibration at idle nad somewhat lower RPMs. As soon as I'd take off with it, the light would go solid again and it seemed alright. I took it to my mechanic when I got back and he was getting codes for misfire in the 3 and 6 cylinder and he said they weren't getting proper fuel. The 3rd was really bad and the 6th was random and somewhat weak. We put a new spider injector assembly in it and it didn't solve the problem. He checked around the intake gasket for leaks and couldnt find anything. Compression in that cylinder is 180 lbs. It doesnt appear to be leaking coolant. He checked the fuel pressure and when I turned the key on a he had right over 60 lbs. It dropped off some after the pump kicked out, not sure how much. I'm confident in his knowledge on this, he's owned pickups with these engines and I had a 96 chevy with the same engine and any problems I had he solved no problem, but right now hes kind of scratching his head on what to do next. I'm not mechanic and I don't know code numbers or anything else but he's got good diagnostic equipment, I just know it was a misfire in 3 and 6. Its got no mods besides a k and n filter and some straight pipes. Any help or suggestions on where to look next would be sweet. Thanks!
could be something as simple as a bad plug wire. a friend of mine had alot of problems with those spider injectors. he got so mad, he finally sold it. hope you get it figured out.
Its got new plugs and wires as well.
did he change the cap and rotor??????? they have terrible problems with the carbon buttons burning away...examine the outside of the ignition coil for high voltage leaks..... look for white dots and dust circles near the external frames.... ignition coils are cheep.... as are caps and rotors...
i just put a used 350 vortec in my truck and have the same problem with the light, the truck drove fine with no noises the all of a sudden the oil pressure dropped and lost all power. went to stop the truck and it died. then starting getting hot. tried to start the truck back and it was like the battery was dead, would even trun over. it cooled off and it started. I replaced the distributor with a alumnium. if it jumped time or isn't timed right would that cause this problem