JCT1990

Well, its coming down to the point where I've gotta have a compression test done because I can't figure out why its misfiring. I dont have the adapter for the 5.4 cylinder heads so I'm just waiting to hear from the garage at this point. Really not looking forward to what its going to cost if there was damage done to the cylinder somehow.

artgarcia

Check the harness for loose contact, check the red look is working properly also agoodseat between the coil and spark

joer1234

I had a real bad shake from mine misfireing so I replaced all my plugs but didn't do my coil packs now my check engine light is on and if I don't let my truck warm up before taking off then it shakes Real bad but it's misfireing in cylinder 8

redblaze71

Guys. Your misfire issues sound exactly like when my '05 was having injector problems. Ford had a bad batch of injectors for 5.4. They will stick open, dumping fuel in the cylinders. It feels like misfiring. As I mentioned in an earlier posting. All of mine were replaced under a warranty that Ford extended to 120000, for the injectors. Then a year or so later they replaced the cats also from all the raw fuel that clogged them up. Check into it. My mileage was horrible for a while, until this was all fixed.

papa tiger

You need to plug in an OBD II code reader, document your codes, navigate the pages offered and document those findings, especially your I/M tests. These tests will OK or imcomplete settings and tell you which parts of your fuel system are malfs. Will give you O2 sensor tests, fuel and evap system tests. Follow your OBD II's nose. It will save you mucho $$$ just replacing parts.

JCT1990

Well unfortunately for my wallet.... Cylinder 4 (the one that was misfiring) has 0 lbs of compression. So now I've got the truck at a different shop to find out why it has no compression.. We're guessing its a burned valve but I wont know until next week.. Still not really sure why this happened but I'm guessing its just bad luck?

To be Continued....

papa tiger

Burned exhaust valve usually means lean mixture on that cyl. If it has a cracked head between the two valve seats, usually means loss of coolant. Your ODB II will tell you of a fuel injector Malf or a O2 malf causing a lean mixture condition. As your injector receives 12 volts when the relay closes the ground is back thru the ECU so look to ground condition if lean fuel injection. Your ground voltage should be above 4.5 Volts with motor reved some. Your I/M tests will help a lot. The ECU usually fails for the whole bank of injectors if the ground wire is good.

JCT1990

Is it possible that from the initial misfire, while the truck was still running that the gas from the injector could be causing the rings in the cylinder to not seal and thats why im getting 0 compression? I heard this from a freind and just wanted to see if its possible.

papa tiger

If that is the case you will have a hole in the piston, and would have heard some bad awful noises with a lot of smoke, blue smoke. Usually a valve fails gradually with a lot of snorts and pops along the way. The longer you run it the worse it seat is and the hoter and more cracked the damage becomes until pieces break off and drop thru the piston or go out the pipe to rattle and blink about some. Some times, more often, it is a blown head gasket between 2 cyls that bring abut a severe drop in compression. Either way it is a tare down if there is no compression/ below 20% of others in the motor. Hope for a head job and not an engine. Good luck !

JCT1990

Yeah thanks, The truck never smoked so I doubt that was the issue. And I guess it would backfire a bit if I revved the motor in neutral but I never really thought anything of it... me lol.