Still fighting the Carburetor Gremlin

JimIsbell

Engine GM 229cu/in 6cyl DualJet Carb.

Putting the "new" Dual Jet on the car in place of the Q-Jet that the PO had mistakenly put on it has helped a bit, but I am still having some problems. They may or may NOT be carb problems so I am looking for some insight.

It runs smooth as a baby's butt some times and at others it seems to be missing a cylinder. I first thought that it was mixture since it was intermittent. It comes and goes. Sometimes it will run smooth for 3 or 4 miles then it goes back to "chug-chug-chuging" on acceleration. When it is cruising at speed it seems smooth, but try to accelerate and it chugs like a missing cylinder. Sometimes it will start and idle very smooth and you could balance a nickle on the valve covers and the next time it seems to be running on 5 cylinders. There are times that acceleration does NOT cause the chug chug and other times it does. There seems to be no rhyme or reason to the changes.

I replaced the spark coil, the dist cap, the plugs and the rotor and set the timing. I replaced the 50thou metering rods with 46thou rods in the carb, that really helped on the starting problem and for a few days it ran smooth as glass but then it went south again. Next try will be spark plug wires but I don't see how they could cause an intermittent problem.

Any suggestions??
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Jim
1983 El Camino

CoyoteOn2 · Posted: Tue Jun 03, 2008 11:34 am Post subject:

Jim, Just a thought, Is it Possable you may have a weak Plug Wire? Maybe bleeding under a load? To me, without first hand knowledge of it's symtoms, that's where I'd start in looking
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rbohm · Posted: Tue Jun 03, 2008 11:46 am Post subject:

one of my college instructors ran across a similar problem with a ford many years ago. he did a ton of work on the car, but couldnt figure out why the car would have fabulous power most of the time, and would stumble all over itself at other times until he got a wiring diagram and found that all the electrical power goes to a single point, the starter solenoid on the fender well. it turns out that the moveable disc inside was loose and it was shorting out on occasion causing the stumbling problem. you might replace the starter solenoid on your car since all the electrical power goes through a single point there too.
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66 mustang
76 el camino

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JimIsbell · Posted: Tue Jun 03, 2008 12:52 pm Post subject:

I don't think its a loss of power to all ignition as it is a Chug-Chug-Chug type of problem...like one cyl that isn't combusting properly under acceleration.

The spark plug wires seem more likely at this point, but I will remember those comments on the starter connections.
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Jim
1983 El Camino

JimIsbell · Posted: Tue Jul 01, 2008 8:27 pm Post subject:

The problem seems to be a leaky throttle shaft. I have acquired a set of bushings to rebuild the carb and will see what happens.
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Jim
1983 El Camino

old_coot · Posted: Tue Jul 01, 2008 10:04 pm Post subject:

If the prob;em was just at idle, I might agree on the throttle shaft leaking but if its doing it at highway speed I would bet against that being the problem----I would still be looking at fuel as in maybe a pin hole in the line from the tank or the little sock filter in the tank being restricted, possible a sticky valve in the fuel pump etc.Also I've seen the wires inside the distributor that are connected to the pickup sensor break due to the flexing from the vacuum advance....................Dan
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