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FDNY 343

55 B85 With EN707 rough running

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I can’t figure out why my truck runs rough and stumbling, chugging whenever I start it and stays running like that for 2-3 minutes then all of a sudden purrs like a kitten and runs smooth like a fine oiled machine. It reminds me of a vacuum leak or something opening or closing when it gets to a certain temperature it activate something and she smooths right out. Anyone have any thoughts or ideas on what to check? Come to think about it, I’ve only started it in the “B” position for batteries and ignition toggle switches on the dash. But that still does’nt make sense. I changed all the spark plugs today.... Heavy Wetish Black soot/crud build up. Haven’t checked or changed Cap/Rotor/Points etc. Truck has been sitting not run for over a year until I bought it a few weeks ago. Anyone else experience this? 

Thanks ~ Jimmy

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Sounds like the plugs you pulled were fouled. Did you check how strong the spark was when you replaced the plugs? I'd look at the ignition system first. 

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37 minutes ago, Dilbert120 said:

Sounds like the plugs you pulled were fouled. Did you check how strong the spark was when you replaced the plugs? I'd look at the ignition system first. 

...and then be sure the fuel system is clean with fresh gas. Then run a can of SeaFoam through it. The other possibility is the valves could be sticking at start up.

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Don't forget to hook up a vacuum gauge to the intake make shure your vacuum advance is working on the dist.

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My LS95 had the same problem, also a 707, maybe it’s differnet but with ours we found out we bent a few push rods due to some bad fuel. I’d check your fuel filter to make sure they’re not gunked up with bad gas. If it’s not fixed soon the problem will compound on itself.

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please let post what was the final problem. did you check the coils? also is it on both ignitions A & B that it happens.

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One more thing simple as it may be is the choke. Yes let us know what you find.

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