Rough Running 1995 GMC Jimmy Has No Power

06-19-2004, 11:35 PM
I have a GMC Jimmy, 4.3L, 4 door, 4X4 with about 113,00 miles on it. It has been a very dependable vehicle for years until a few days ago when the check engine light came on and it started running real rough. A few weeks before the light came on, the catalytic converter had a rattling noise that developed inside of it and then one day after driving, I started it up and a white fowl smelling smoke came out of the tail pipe which only lasted a few minutes and has not happened since. The day the check engine light came on I had been helping a friend move and had been towing a 5X8 U-haul. The truck ran fine pulling the trailer empty out to his place but after loading it and getting back out on the road the truck could barely pull the trailer and then the check engine light came on. Knowing the muffler needed changed anyway I replaced the entire exhaust system including the catalytic converter. The old cat's honeycombed insides were fractured and some of the magic poured out the end when inverted making me feel better about paying the near $300.00 for the replacement. I had also changed the spark plugs and ignition coil at the same time. All of the spark plugs looked normal except for the ones that came out of cylinders #1 and #4, which looked fowled.
With all these repairs the light remains on even though I also removed that battery cable to erase any problem codes...One other thing I noticed while troubleshooting which is very weird is that when the truck was running in this rough condition if one of the spark plug wire was removed the engine ran much smoother.....anyone have any ideas ????

06-20-2004, 01:32 AM
several issues it could be is 1.Cpi is bad leaking fuel 2. EGR valve is clogged with chunks of carbon 3. Oxygen sensor. Mine had the first two problems. Installed a new Cpi and made a screen for the EGR valve gasket and now everything is A OK.

06-25-2004, 04:43 PM
Well, trying to keep the troubleshooting costs to a minimum, I replaced the O2 sensor and removed the EGR valve to check for carbon buildup(it looked good)....but the problem still persisted. I even removed the plenum sensor under the "Vortec" name plate to look for passages that were "too clean" and found them to be good and dirty....
I ended up taking the Jimmy to a trusted dealership here in town and they found was the distributor cap causing all the problems....Whew....Just thought I'd share my experience. It's nice to have my Jimmy bacK !!!!

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