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My 1996 F350 with a California Emissions 7.5, has had a miss in #5 cylinder for a bit. It does not smoke, uses a little oil(quart in 3000 miles) has 16 inches steady manifold vacuum, compression is lower than other 7 holes(115 compared to 145). Sets CEL with DTC P0305(misfire detected #5 cyl). When ambient air temps are real cold, under 45 degrees, when first started, you can hear a slight piston slap, which gradually decreases as it comes up to operating temps. Engine idle is very slightly rough, engine accelerates smoothly with no hesitation or apparent missing. The question I have is this: when I pull the spark plug on this cylinder, the plug looks as though it was just installed, no color, no oil, no unburned fuel! I played with it again this am, and felt all 8 injectors with engine running, all make a pulsing vibration, so it appears all are functioning, so why is there no color on plug?? Truck has 148,000, had new cat and muffler last year. Only problem I have had is I have had 2 rebuilt distributors fail, in the 3 years I have owned it, both failures were PIP sensors, now have a good used distributor with a new Motorcraft PIP installed. I think the distributor failure is what hurt the engine, as it sounded like a bunch of crossfires when it failed on Interstate 40. New engine on the way. Thanks for listening to my rambling! Dale
The spark plug from the #5 cylinder probably doesn't look bad because the cylinder isn't doing any work. To me a quart every 3000 miles is a lot of oil usage and it will probably ruin your new catalyst.
How do you know it is a piston slap that you are hearing?
__________________ 2013 F150 FX4 5.0 Super Cab 3.55 SnugTop BedRug with a futon, blue bed lights, and a Marlin 45-70 Guide gun with 425 grain bear stopper rounds 1967 F100 Ranger Camper Special 460/C6 D3VE heads, unkown mild cam, Weiand Stealth intake, 1" spacer, Edelbrock 1407 750 cfm carb, Assualt Racing HEI dizzy with DUI coil and module and Moroso curve kit 1969 F100 360 4 speed project truck
Well, when the engine is cold, say 60 degrees or so, after the engine starts, you can hear a noise that sounds like some gravel being shaken in a can. And as the engine temp comes up, the noise goes away. Thanks! Dale
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