murphys223

i have a 97 f150 with a 4.2 L that misses on one cylender it will barley hual itself the engine light flashes as well i have checked the fire on all the wires and they all seem to be firing i am totally lost as to what to check next it has an automatic transmittion and the heads were taken off and new heads put on as well as all gasgets i have changed the plugs and distribution unit for the wires and no headway made at all does anyone have any ideas? the next thing i thought of was a compression test but it should have great compression

Davescort97

First off find out which cylinder isn't firing. Do this by pulling the wires out of the distributor one at a time. When you get to the cylinder that isn't firing there will be no change in the sound of the engine. Don't pull the wires off the spark plugs you will get shocked. When you find which one(s) aren't firing check the plug for gap. Check vacuum hoses for leaks close to that cylinder. Check the compression you may have a bad valve or a broken compression ring. Switch wires and see if the misfire transfers to a different cylinder.