Help 4.3L runs bad

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  #1  
Old 03-31-08, 05:40 PM
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Help 4.3L runs bad

Well guys the unstoppable jimmy isnt doing to good. This is the first time I have ever had trouble with it. Its over 180k last I looked but always ran great. Today it started running bad and lower rpms and no power. It even sort of vibrates like its running on 4 or 5 cylinders.

It still starts up right away but at any rpm even idle it sounds like its not running on all 6 cylinders. Oil pressure is fine.

It also now sounds like there is a hole in the exhaust. I never seen a hole in the exhaust but as soon as the louder exhaust started is when it ran bad.

Its a 1992 GMC jimmy 4x4 with a 4.3L and anto tranny. Its been raining out so I havent had time to really look into anything.

If anyone has any suggestions on whats wrong please let me know, I would appreciate it.
 
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  #2  
Old 04-01-08, 02:40 AM
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When my 4.3 chevy engine started doing that, it was the plugs and wires. I also replaced the rotor and distr. cap at the same time. The wet weather may be a telltale sign that you've got moisture in the distributor.

Pecos
 
  #3  
Old 04-01-08, 06:55 AM
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Thanks Pecos, I'll try to get out there if the rain holds off. Everything lookes nice and dry so I didnt think it was moisture making the spark jump from the wire but it could me moisture in the cap. Im going to pull all the plugs today and check them and if I can maybe replace everything like you did.
 
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Old 04-01-08, 01:43 PM
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4.3 runs bad

It could also be a bad spark plug. Bad spark plug wire. Bad lifter. Bad Gas! Several things. Water under cap or bad cap.
Even a bad vacum leak can cause a big Problem. I think if memory is correct, it should have throtle body with vacum line out of back.Some where plastic,if so look there. This will go bad and cause same problem. Also stop up under throtle body.Could also be bad Ing. mod. Does it pop or back fire through throtle body? .Have you have ever replaced plugs or wires, rotory button or cap?Did it come on just now, or over time. I would pull plugs, and ohm wires, check cap and button first.You can get ohm readings for a repair manual,for wires.If all else fails, get it on a scanner.It will help pin point problem.
Hope this helps.I turned wrenches for years.

 
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Old 04-01-08, 03:06 PM
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In order, this is what -I- would do, to (hopefully) save time:

Make sure firing order correct, and nothing shoved up the tailpipe - if any chance anyone could have fooled with vehicle for April Fools.

Pull the plugs and analyze, including carefully looking for carbon tracking possibility and cracked outer or inner ceramic insulators.

Make sure coolant not mysteriously disappearing in engine due to gasket failure.

Ohms test plug wires per suggestion.

Observe under the hood while it is running, at night to see if any stray sparking.

A compression test.

..........Then I'd move on from there.
 
  #6  
Old 04-01-08, 05:11 PM
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I ordered new plugs, cap, rotor and wires today. Ill put them on tomorrow when I pick them up. I tried to look today but cant see much without removing air cleaner. Ill look around and check everything out tomorrow. I had it for almost 4 years now and never changed these. I stopped at a gas station and put some gas in it and it felt sluggish so I kind of thought something was wrong. That was about 15 min before it really started running bad.

Today it started and ran ok but still sounded like it wasnt firing on all 6 cyl and when I put it in gear it really ran bad. Im not driving it until I get it fixed.
 
  #7  
Old 04-01-08, 06:45 PM
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If it ran worse after you put it in gear! It's a plug or wires. Check PVC also fuel filter, part of a good tune up.
Good Luck!
David C

 
  #8  
Old 04-02-08, 02:14 PM
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I changed the plugs, wires, cap and rotor today and found the problem. I think some how the plug wire in teh center plug on teh drivers side popped off.

It seems to run fine now, those spark plugs needed to be changed anyways. All the plugs looked good, no white ones and none with a buildup on it.

It was a pain in the butt to change the plugs but I got it done this morning.

Thanks alot guys
 
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