Hello, new to the forum. Anyhow have a 02 f150, 5.4. Engine Started missing the other day, threw code p306 so cylinder 6 misfire. It does have spark (after putting in a new plug and ohming the coil, and using a spark tester). Figured it was the injector and installed a new one, but still missfires. So i started checking voltage and it gets maybe 3 volts with engine running, but 12v when the key is on but not running. The other injector next to it gets 12v when key is on. I also unplugged random injectors and it ran worse, so i know for a fact its only cylinder 6.

So basically only one injector is not getting voltage. (Inj wires are not grounded either, so i wouldnt suspect faulty harness). Could this be the pcm? Crank position sensor? Cam sensor? Odd that its only one cylinder being affected.

Thank you for any help.

 

I would say it is your ECU.

 

Have you actually tried swapping coils?

 

I will certianly try swapping coils, and im actually hoping its the pcm since the crank sensor is behind the ac pump.

Planned on bringing to a shop to see of they could scan it, maybe they could detect if it is a crank sensor or not. Idk just weird that its only one cylinder.

Theres also the dash scan function thing and a few codes popped up there, have to look them up

 

The other thing to look for is corrosion, especially since it's a 2002.

Pop the connector off the pcm and look at it. Look at anything pertaining to the ignition system that feeds to the coil.

You might get lucky and it's just a loose connection.

I would also recommend what glc is stating. If that code goes to another cylinder, then you'll know it's the coil.

 

Since it is only one cylinder, I don't think it would be the sensors.

 

Success! Ended up being a bad coil, swapped it to another cylinder and made that one dead. Weird that it still sparked and ohmed correctly, must have ben a tiny crack in the boot or something. Super happy.

definetly in need of a tune up, will replace with accel coils and motorcraft parts. Thank you for the help

 

Looks like glc's advice was right on. Glad you got it fixed.

 

Congratulations on finding the problem.
Around here the advice on coils is to buy Denso, Delphi, or Motorcraft. Denso makes Motorcraft. There are lots of substandard coils out there. rockauto is a good source.

 

Do NOT use Accel coils.