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73-87 Chevy _ GMC Trucks => Performance => Topic started by: tierraverde on July 23, 2002, 09:39:00 PM
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I have an '85 454 7.4 liter dually that runs awful when first started up--it blows black exhaust and sounds like a boat (chug chug chug). My husband just replaced the EGR valve and it warms up a bit faster, but still the black smoke. Once it warms up it runs great. We're thinking it needs a new carburetor. Any ideas? Thanks!
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Well, I'd check to see if it's backfiring first, because it kinda sounds like that's happening. That's usually caused by old spark plugs, or bad wires in the plug lines or distributor. Although I'm not an expert, I'd check that first, just to be sure.
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Sounds like too much fuel, check the carb and check for vac leaks. If all looks ok, time to overhaul the carb.
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It backfires only occasionally, and then it only does it once.
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It does seem to run rich (I can smell gas). We had our mechanic fix a clogged jet awhile back and he said he couldn't get the carb to run right. The problem started about a month after.
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too bad you dont live in cali, i have rebuilt many Q jets. you need to have the carb replaced or rebuilt. im sure it has a lot of miles on it. probably a combo of oil and fuel for the black smoke.
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Where's Cali, CA.?