Constant Missfire

[lincman29]

I have an 06 xlt with a 5.4. I keep getting p0303, p0012, and p0021 codes. I've changed both cam sensors, both vcts, plugs, coils, injector on number 3, and both o2 sensors on bank 1. It idles fine and no diesel noise. Has a light misfire at idle and then dies when you put it in drive or reverse. Struggles around 50 mph when it gets hot, but drives fine when cruise is used. I'm stumped and don't know what else to try. Thought may the cats are gone, but I get no code for them. Looking for any kind of help. Thanks

 

[1955moose]

Have a muffler shop or a repair shop pull your rear o2 sensors and check pressure with the screw in guage. I've been told my 2000 4x4 5.4 might have one or two plugged cats. My symptoms are loss of power on hills and horrific mileage 8.2 to 9.3 mpg. Good luck let us know what they find.


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[lincman29]

I unhooked the muffler last night and a lean on bank one. There is something wrong with cylinder 3. I've changed plugs, and coils three times already. Keep getting misfire on that one cylinder and timing over retard and over advanced. I started a compression test and 140lbs on that cylinder dry. Same as number 1. Probably need to do it again. Battery was getting weak since it's been sitting a while.

 

[stamp11127]

Lean codes are usually caused by cracked manifolds or leaking gaskets, not issues with the cylinder.
Variations in timing can be caused by worn timing chains, sprockets and guides and possibly low oil pressure to phasers.
You can check the temp of the cats, one that is plugged will have a very high temperature.

 

[bc11]

You could check for a wiring issue perhaps in a connector in the injector. Get a noid light set from Oreallys which are returnable for refund within 48 hours as a loaner tool. The gm tfi noid light will fit the ford connectors and the ford one doesn't. The noid light will flash just like it should be firing. The 303 code could be the cop or the injector. If it was wiring on the cop then it would likely throw a 353 code for #3. Those connectors are in tight places and subjected to twisting and moving that may break or touch. Wiring can get melted on things like ac accumulators that get hot. Test all of them for a comparison.

 

[Lostneye]

Cats don't typically wear out unless run overly rich or lean. And they shouldn't affect how the engine runs except if plugged up. If the COP/plug/boot is good on cylinder 3(try swapping with another cylinder) then look at the injector.

 

[lincman29]

It's been awhile, but misfire went away for a while then came back on number 3. Still getting p0011, p0012, p0021, and p0022. I've changed both solenoids and cam sensors. I hope it's not the phasers. Thing is it runs great at idle when you first crank it up, but once it warms up it runs ruff while in gear. Runs fine in park. Any ideas????

 

[toadeyes]

It could be a simple leaking vacuum line or hose, check for any crack or worn hose and replace them.

 

[1955moose]

I agree with toad eyes sounds like an intake leak. You can try by yourself, or bring to a shop that has a foger. Wherever the leak is it will come out from that spot. A friend of mine failed smog on his 88 escort, the foger showed it was coming out the throttle shaft on the throttle body. Most vacuum leaks get worse when warm. The injection is running richer when cold, so the roughness isn't as bad. Good luck, keep us posted what you find.



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[nsperf]

Check for vacuum leaks at hoses lines and any other vacuum location including the intake and intake to head mounting.

You have a couple of options to test.

A use a can of brake cleaner and lightly spray around areas and listen or watch for the engine rpm to pick up and or smooth out.

B use an unlit propane torch, turned way down and again wave over and around areas and listen for engine rpm to pickup / smooth out.

Im sure I don't have to mention this but do this outdoors.

 

[lincman29]

I've changed everything with the battery still connected. I clear the codes, but they cone back. Truck runs good, but still getting the codes.

 

[jhz563]

did you ever get this figured out?

 

[1955moose]

Did you ever get a chance to run a fuel pressure test? I was reading about another member that had a crumbling fuel line in tank that hooked to pump. Was sucking air making it run lean. You've gone this far, fuel pressure is real critical on performance. Let us know.


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