Jimmy Problems

Asked by Feb 11, 2011 at 10:46 PM about the 1994 GMC Jimmy 4 Dr SLE SUV

Question type: Maintenance & Repair

ok....i am a honda kind of guy.  know the ins and outs all the way around, but i just bought a 94 jimmy with the 4.3 vortec cpi.  the guy i bought it from told me that it was running rough and shifting hard.  thought it might be a vacuum line so he said.  so i get the car home and i start checking it out.  first changed plugs, wires, cap, and rotor. absolutely no change in the start or rough idle.  it would start after 2 or 3 shots of ether and would run but run like crap.  so i started going all the basics of making a motor run.  fuel, air, and spark.  had spark and air but didn't have good fuel pressure.  i could prime the pump about 6 or 7 times and it would start.  so i changed the filter and pump.  put everything back together and the truck would start right up but still idled rough and when i tried to drive it it was like it was struggling.  checked pressure again and have 61psi with virtually no leakdown.  it also still had a miss to it at idle speed.  i rememberd an old trick my dad showed me on his truck which was to adjust the distributor..... advance or retard to get where you need it to be.  played with that for a little bit and kind of got it smoothed out so i started checking to make sure i had fire at all of the plugs.  one by one i disconnected them to see if there was any change and there wasn't.  when i got to the number 3 and 5 plug i happened to brush against the knock sensor and the motor smoothed out tremendously.  played with it a little bit and realized that the ceramic inside the sensor had broken.  i pushed it in as tight as i could and took it out for a test drive.  to my suprise i had full power and the truck ran like a scaulded dog.  so tonight i stopped and bought a new knock sensor and installed it.  after i put it on i adjusted the distributor back to the position it originally was in and tried to start it.  truck fired up but i had to fine tune the distributer to get it completely smoothed out.  got in to do a test drive and it died before i could get out of the driveway.  started back up and pulled out and low and behold the truck was back to its sluggish ways.  no power, foot to the floor, and the dang thing wont move over 20 mph. finally changed the iacv, and the ignition coil tried to start it again and all it does is start and either run rough or die.  i am getting pissed and ready to take it to the junk yard.  PLEASE HELP ME!!!!!!!!!. i only have til sunday night to get it running again i need it to go to work monday.  please tell me whats going on.

1 Answer


damn man that seems like a bitch, im a tech at a shop in west chester and i would suggest doing a few things, id first buy some techron fuel system cleaner, if those are original injectors i wouldnt be surprised if they were alittle junked up, try that and see what happens that shit works like a charm for my lexus, if it doesnt i know those jimmys have a idle air temperature sensor, if thats reading false on you by saying its bringing in warmer air than expected it could throw the idle and acceleration off because warmer air is denser with less oxygen, it could b thinking its getting this air fuel ratio from what its bringing in but really its colder with more oxygen so the mixture could be extremely off and its trying to compensate for it off the MAP and throttle control, let me know how it goes bro, GL!

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