I've got a 2007 f150 with the 5.4 3v. I am having to what appears to be a misfire. Things that have been done (in order) new battery, throttle body and MAF cleaned, fuel injection service, power steering fluid changed, coolant changed, spark plugs changed by the local dealer, and all 8 COPs changed. The misfire happens from around 45 to 50 mph (1100 to 1300 rpms). After i had all my plugs changed, ran great for about a week or two, then threw a cylinder 5 misfire P0305 code at 75 to 80 mph in overdrive. That is when i changed all the COPs. Misfire is gone at 75 mph and beyond, but still present at the 45 to 50 mph range.

Is there any way the cylinder 5 misfire could have messed up the spark plug in that cylinder, or is that just wishful thinking?

Thanks in advance,
Jordy

 

Could be a bad plug also.....that can happen.....

 

Time for a new Plug and a new COP just to be safe.

New plug could have a small crack and new COP's can and do go bad.

 

I'm going to change cylinder 5 plug and coil today and hope for the best. Any special precautions I should take when removing the plug? It has been on there about a month or so.

 

You could also try switching the #5 COP with another cylinder and see if the misfire follows the COP. Then you would know if the COP is the culprit.

Kev

 

No lucking in changing cop and plug on cylinder 5. A code would be nice at this time

 

I had same issues with my 05 5.4. Did all that stuff too and ended up being a leaky fuel injector.

 

how did you determine it was a leaky fuel injector?

 

I was tired of messing around with everything myself so I took it to the dealer and they diagnosed it and replaced. It was under the 2005 injector extended warranty so it was free. I don't know if there are problems/coverage for a 2007. If anyone knows please chime in. I would like to know as well as I just purchased an 07.

 

I believe it was just for the model year 2005 as they had defective injectors that could
stick open and hydrolock the engine.

 

you can pull the fuel rail leaving the injectors attached to the rail and turn the key on-engine off and see if any of the injectors are leaking.
If you end up needing injectors let me know. I have a low mileage set from a 2007 that I do not need.

Kev

 

is it very involved to pull the fuel injectors?

 

Not too involved. There is is 2 bolts that hold each rail down. Passenger side there is more hoses in the way so might have to work around that stuff. Drivers side is fairly easy. Put some clean shop towels under the injectors and turn the key on but do not turn the motor over. If you see fuel leaking or fuel on the shop towels then you have a bad injector. Try to pull the rail and injectors straight out. Use a some clean motor oil on the o-rings when you re-install them.

 

well, no leaky injectors, i'm going to get another cop, try it on each cylinder individual, and see if i can narrow it down, if that doesn't work, they change the plugs again

 

well after a little one on one action with my truck yesterday, i decided to change my plugs again! did cylinders 1 through 4 first, everything went smooth, then cylinder 5, everything went smooth, then on to cylinder 6....... i put the 9/16" swivel head spark slug socket (made the entire job an order of magnitude easier) and it felt like the ratchet was stripped. The plug was so loose, i unscrewed it completely by hand. Cylinder 7 was almost the same way, and then cylinder 8, i had to get the 1/2" ratchet out to break it loose. So after a month or so of chasing a misfire, all it was a couple of loose spark plugs. In the end, new COPs, and new plugs, and most importantly, she is running like new again (finally)!!!