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Unread 05-23-2002, 09:32 PM   #1
retnav94
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Join Date: Apr 2002
Location: Lemoore, CA
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Rough Running Engine

Need some brainstorming. I am limited in my mech knowledge so i would like to throw some things out there for some advice. I bought a 1985 cj7, 258 with everything standard engine-wise. No modifications. I initially drove it, it ran fine for a couple hundred miles. I had a shop look it over, because I heard a knocking. They timmed it and rebuilt the charcoal cannister, and tweeked a couple minor things. I changed the plugs, dist cap, rotor, plug wires and thermostat. I also changed the timming chain/gears, and timmed it to specs. After no more then 30 miles the jeep runs like crap, and sounds even worse. We checked the compression, and all six were good, however, the plugs are black.

I suspect there may be big problems. My question is about the carburetor. If it is shot, would the engine knock badly? I am thinking that is the first thing to check. Also I understand that no after-market carburetor is legal in CA. Any advice would be greatly appriciated.

Gary

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Unread 05-24-2002, 11:15 AM   #2
johny1i
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The carburetor won't cause a knocking--symptoms of a bad carb would be more like it won't idle, surging while going down the road, terrible gas mileage, hard to get started in the morning, etc. I know this sounds kind-of dumb, but are you talking about a "tapping" or a sure-enough "knocking"? A tapping could be something as simple as a lifter, which could affect the valve, making the engine feel like it is running on five cylinders/missing, etc. Mine did that for a while because it had been sitting before I bought it, then it got better and now all I hear is an occasional tapping when the engine is cold. However, yes, a knocking could be much worse than that--as in a rod bearing going out. However, the only experience I have with that was an old '65 Impala and it didn't make it more than just a few miles before the engine was shot. Not something that went on for a long time like you're talking about. Mine could have gone all at once, though, so see if anyone else on here has had experience with rod trouble. That's all I know
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Unread 05-24-2002, 11:17 AM   #3
johny1i
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forgot something--how many miles does it have on it? A high mileage engine could have bad rings (too much blow-by), which would explain your fouled-out plugs. This wouldn't cause knocking, but it could all tie in together if the engine is worn out.
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Unread 05-28-2002, 07:55 PM   #4
hollywood
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Chect the PCV valve, and the EGR valve - both can cause poor idle and rough running.
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