I have a 2005 f150 with the 5.4L I did the plugs at 70k and 7 of 8 broke. The only plug to not break was cyl 6. at 75k miles my trans lost 1st and 2nd gear so i had it repaired at a shop down the street to the tune of $1800. Now at 76K miles, I have a misfire in cyl 6. and it gets REAL bad at 75mph. As in, it will barely hit 80mph and limits itself to 3000 rpm and the check engine light flashes. I also have a rough idle, but i figured its cold + crappy winter blend fuel + edge tuner...

OK, so i searched and doing the search thing, i found that usual cause of 04-08 5.4L misfires is injector or COP. So I replaced injector and COP on cylinder 6 since i was getting p0306 and another code for "misfire in first 1000 rpms. Reset codes, and Codes came back, took off edge tune (left it hooked up since it is a code reader however), reset codes, and codes came back. swapped injectors on the other side of cylinder 6 (injectors 1 & 2). Reset codes, and codes came back. bought a new spark plug for cyl 6 since its the last thing i can easily replace and I got this when i pulled out a spark plug with 6000 miles on it....


So i thought to myself (NO WONDER IT RUNS LIKE CRAP!) replaced the spark plug, reset codes. Codes came back. Unplugged battery for an hour, and the only thing that accomplished was losing my presets on the radio, reset my tripset, so i cant tell exactly how bad my gas mileage is, and it took a bit longer for the codes to come back.

I have not ventured into checking the other plugs (honestly i'm a bit frightened what they might look like), but seeing the plug from cyl 6 was ""

Now that i've replaced everything i can on cyl 6 and the problem is still there, i'm curious whats wrong with my motor that it would burn up a spark plug like that in 6k miles.

I put in synthetic oil and a new filter every 5k miles, just did air and gas filter pretty recently.

Am i missing anything? I have another truck, but it runs worse than this one, so it is my only form of transportation.

Any help/ideas/suggestions would be greatly appreciated.

p.s. job offers in southern states would be looked at with great interest at this point. Anyone need a machinist/welder/fabricator?

 

What kind of jobs you looking for? I work for a company in Fort Worth, TX that designs and builds oil field equipment. We have signs posted for welders (must be certified i believe) and fabricators. The shop guys are getting about 60 hrs a week right now. Production capacity for 2011 is overbooked.

Oh and you might want to do a compression test on that cylinder. Is the truck loosing any oil between fill ups?

 

I did the oil and plugs at 70k, oil again at 75k, tranny at 76k, and this just happened at 77k, so i honestly haven't even checked the oil since i just changed it 2k miles ago. i will look into that and the other plugs hopefully tomorrow.

Thanks for the reply and the job tip!

 

Any update? I'm having a very similar problem (2k6 5.4l 43k mi). Codes were p0171 and p0306 for awhile (and P0305 if pushed hard), but lately just getting just P0306.

Had a vacuum leak on filter box seal. Fixed that and replaced MAF w/ new motorcraft MAF.

Put UV dye in coolant but haven't found anything.

Searched for vacuum leak w/ starting fluid a couple times, also tried propane - nothing.

About to replace coil. Real hesitant to touch the plug. Maybe I'll do injector first instead (I'm assuming they don't break as easy?).

Pulled driver's upstream O2, sprayed w/ throttle body cleaner and replaced. Plan was to swap O2 to passenger side but I can't move my torque wrench far enough to loosen it.

Bought this thing 2.5k miles ago....ughhhh

LIke you, I'm sick of winter(northern NY). Working in an icy driveway really sucks...

 

I have a 05 5.4 that has been giving me mis fire codes for some time now. The gas milage whent down under 10 mpgs and would skip under a load on the high badly. It sound like you are haveing a similar problem. I did injectors,plugs, o2 sensors and it still had the problem. I check the plugs after 7000 miles and I had two that where even worse that yours. I did all 8 plugs again and it seamed fixed. The milage went up to 14-16 mpg but after just a few hundred mile the milage started to drop off and just got another miss fire code. I have been fighting with this for close to a year. I am bringing it back in tomorrow and pulling the plugs to see what they look like. Have you had any luck with yours? I want to do a compresion test put it seams to have a odd size hole. Does anyone know what i need to complete a compresion test? HELP.

 

I suggest you perform a compression check on all cylinders but if you can't afford to do all at least #6 and one other that you don't suspect to have any issues. The way that plug looks I suspect you might have a bad exhaust valve or possibly something going on with your rings on that cylinder. You have already replaced all the suspect items( COP, plug, injector ) on that cylinder so it's time to dig a little deeper. I would also thoroughly inspect the connectors for the COP and injector to make sure they were not damaged during the maintenance. The COP harness connector has a seal inside it to keep out moisture and it can tear and push into the bottom of the connector if you not careful and prevent it from seating properly. This will cause the misfire your getting and also cause the plug to foul quickly due to lack of proper ignition on that cylinder.

 

Dam I just noticed the OP was back in 2010. I hate it when I do that.