Backfire
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New User
Joined: Apr 2004
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Backfire
i have a 78 f150 4x4 i just bought a couple months ago it ran great when i took it in for a tune up (oil change plugs fuel filter ect.) but when i brought it home the oil pressure switch went out and it started backfiring while driving between about 1600 and 2000 rpms and that is the only time it backfires weve checked timing adjusted carb new wires plug wires dist cap and rotor new coil and still backfires we're at a loss any help would be greatly appreciated ...........we were thinking maybe the spark plug gap or maybe they had cracked one im not sure of the engine size but the guy i bought it from said it was a 351w and i know its not the original engine he swapped it so please any help or advice because everyone i work with are chevy guys and giving me a hard time
Senior User
Joined: Apr 2004
Posts: 172
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From: I live in Calif. near S.F
jitter1976, how many miles is on the motor ? if its 80,000 plus , warm up the engine to normal temp. then pull the spark plugs and check your cyl. comprission , your manual well give you your spec's. ,check each one the same way, say you have 150psi ,all but one is 135psi, put about an once of oil in the s/p hole and ran the test again on that one, if it stays the same you may have a valve problum ?
