92 jimmy 4.3 vortec running terrible

I have had problems with my jimmy for the last 2 years one thing after another. This time it is running terrible, the idle is very rough and driving is worse. When I try to accelerate it hesitates and sounds like it wants to go, after a little bit of this it accelerates like it normally would with the pedal floored. I have done all of the ussuall stuff. new plugs, wires, distributer cap, roter. I had a problem with the oil about a mont ago. It turned to sludge after like 1000 miles and it clooged everything up....I replaced the oil filter and cleaned out under the valve head cover getting all of the junk out of there. I have since then giving it 2 oil changes just to keep get any junk left over in the oil out of it.

What is going on? Why is it running like crap? Any help would be great.

Check fuel pressure first, scan it for proper sensor inputs also. All basic diagnostics here.

I just checked the fuel pressure and it was slowly declining. I replaced the fuel injector but it is still running terrible.

Did you replace the fuel pressure regulator? connected to the spider injector.

All of the symptoms that you're describing, the driveability issues and the sludge oil, could be related. If the intake manifold gasket has an internal leak, it could be sucking coolant into the combustion chambers and also leaking coolant into the oil.

Find the Assembly Line Diagnostic Link (ALDL) at the lower portion of the dash to the right of the steering column...it's the connector for checking Trouble Codes. Maybe the computer "remembers" something to lead us to your problem.
Jumper the 2 top right holes with a piece of wire or even a paper clip then turn the keyswitch on. The Check Engine light should flash once then 2 times...1-2 or what's refered to as a condition code 12 which is the computer's way of letting you know it's now in diagnostic mode and is preparing to flash more lights in 2 digit sequences. It'll flash each one including the aforementioned code 12 three times. After it gets through, it'll flash the code 12 again letting you know it's played all the stored codes.

I have had problems with my jimmy for the last 2 years one thing after another. This time it is running terrible, the idle is very rough and driving is worse. When I try to accelerate it hesitates and sounds like it wants to go, after a little bit of this it accelerates like it normally would with the pedal floored. I have done all of the ussuall stuff. new plugs, wires, distributer cap, roter. I had a problem with the oil about a mont ago. It turned to sludge after like 1000 miles and it clooged everything up....I replaced the oil filter and cleaned out under the valve head cover getting all of the junk out of there. I have since then giving it 2 oil changes just to keep get any junk left over in the oil out of it.

What is going on? Why is it running like crap? Any help would be great.


If it has a rough or bad idle check the egr valve for a carbon ball stuck under plunger.

Does it run very god after you get the rpm's up on the road?

i also own a 92 jimmy .

when was the last time you replaced the pick up coil inside the distributor ? very common on this motor - it will give you a miss and haesitation on light throttle from a stop and same at cruising speed but step on the gas and evrything is ok ( usually) . pull the dist. cap and look for green on the ign. module screws or alot of rust . if you see that on the module screws you can bet corrosion has found its way to the pick up . i do mine every 50,000 since i launch my boat in salt water - it was a " mystery miss " that caused me a few grey hairs one weekend , testing it is almost useless and since the part is so cheap -10 bucks - i just opted to replace it and the miss is gone.