gammer

I have an 2001 F150 4x4 with 271 000, I had this brob for awhile, code that comes up is "P0 305", I put a new coil and sb, sometimes it works all right other times it feels like the front end going to fall off it misses that bad, the injector ohm reading is good, I'm woundering if the sparkplug is threading in far enough, because it seems it is only going in about 5 or 6 threads it doesn't seem that it is bottoming out, it's a tapered plug I'm wondering if someone can confirm this for me. Thanks in advance.

ktmboyz

I would think if the plug was the problem it would do it all the time and not intermitently.. Try to put a small amount of grease or never seize on the taper of the plug and screw it in and tighten it, if its sealing it will take the grease off... sounds like a intermitent injector problem.. I have seen a few fuel pressure regulators act up from rust in them and drive the fuel pressure way up to like 70+ lbs and cause a misfire. Take the snap ring off and pull the regulator out of the rail and see how it looks.. then swap the injector with a different hole and see if the misfire follows it.. takes a littler more labor but its better than throwing parts at it

olredneck

I have a 98 with the 5.4 (@#$#@! deep set plugs!) and have had problems with various cylinders misfiring. The solution? My father eventually figured out that the misfires started the day after it rained/had 98%+ humidity. I carry a can of the quick drying electronic cleaning spray for new skips (LIBERALLY sprayed over the coil and down the wire into the well (and across any other wires I see just for fun...yeah, my wife thinks I'm nuts, too) which tames the problem for the rest of the day. The permanent fix has been a felt washer and a plug of silicone caulk around the problem wire just under the coil. Makes the next tune up an adventure but this little bit of redneck engineering has taken care of the skip on each cylinder that's given me a problem. Yeah, I tried the 'new plug, new coil, three bottles of injector cleaner run through the tank' solutions which had limited utility. Just make sure it's not skipping when you seal the well or you'll seal in the problem.

-Farmer tans forever.

ktmboyz

try oem wires and you shouldnt have a problem. If you do there is something wrong