I have a 2005 ford expedition with the 5.4 it has 186000 miles. It developed a misfire and studder running between 50 and 65 miles an hour. Fuel pressure is perfect. I changed the fuel filter. Installed new motorcraft plugs and all new msd coil packs still has misfire and studded. The code pulled some sort of short on the #3 injector so I put a new injector and pigtail on it. It ran great for a day and is back to doing the same thing again. Installed new pcv valve and incident help. Installed new knn air filter no change but I didn't figure it would. I've had it at two ford shops and a local shop and no one can seem to find the problem and I've put over 700 in it trying to fix it. Does anyone have any ideas?

 

Any codes now?

The 2005 5.4's had a bad batch of fuel injectors, I'd consider replacing them all. Also, MSD coils don't have a good reliability record, you can't beat Motorcraft.

How did you change the PCV valve? The 5.4 3 valve doesn't have one, it has a fixed orifice in the valve cover.

I'd also put a standard dry air filter in it, the oiled filters can foul the MAF sensor.

 

The pcv valve pulls out of the passenger side valve cover on mine. It may be called something different that's just what I told the guy at the auto parts store and he gave me the same piece. I'll remove the air filter and replace with stock. Hopefully I can replace some of the mss with the originals I don't have the funds to purchase a complete new set.

 

It's pulling a code for a number 3 injector but it's been replaced with a new one along with the plug. And it only misses between 45 and 55 or under a load. If you kick it up to 65 or turn the overdrive off it won't miss at all.

 

You sure you have a 2005? You sure it's a 3 valve? What's the 8th character of the VIN?

Did you replace the plugs yourself? If so, what do they look like?

3 valve:




2 valve:

 

It's an 05 and has the 3 valve. I replaced the plugs myself it took the two piece plugs at 13 bucks a piece.