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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: joesgarage71 on August 19, 2007, 05:25:48 PM
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I'm still having problems with the 86,She lays down when under a load (going uphill) most of the time. Some time it runs good. I had the factory carb rebuilt and it still done it, I replaced the carb with a 78 Q-Jet. Still lays down.
I had the modual tested by two different stores,I replaced the plugs, wires, dist cap, rotor, I set the timing. The vacuum advance is working good. It has good fuel pressure. I doesn't pop or cough it just slows down no matter how much gas you give it or what gear you change to.
I'm starting to think the computer is bad.
1986 C-10 305-4 bbl/Th350 98K miles
Steve
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Put a vacuum gauge on it and run the hose up through the cowl. Tape it right ot your windshield and take it for a rip. Does it do it when it's cold or just when it's warmed up? What did you set the timing to? Did you check the centrifugal advance?
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It does it when its warm. the timing is set to spec. It has 16 in of vacuum at idle. The mech advance weights are free and have full movement. What am I looking for with the Vacuum gauge?
Steve
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You should have better than 16inHG at idle. Try to advance the timing and see what it does. Are you sure you don't have a kinkied fuel line somewhere? With the vacuum gauge that can help you pinpoint several problems....from timing to restricted exhaust. Try advancing the timing first.
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Not to butt in, but the restricted exhaust idea might just be what's going on. Plugged cat maybe?
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or sticking flow valve in the RH exhaust manifold, if it is stock.
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I would bet my money on a plugged exhaust system.
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It doesn't do it all the time, I removed the cat and the valve is open.That was the first thing I thought of. I have to work today but will do the vaccuum gauge later today.
Steve
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I hope you find a vacuum leak. If that's not it, the trans might be the next place to be suspected.