I posted this as a reply to another thread (I'm new here) and realized that a new thread would be higher traffic... anyway....

I have a '98 F 150 w/ 5.4 at 99,600 miles. I just replaced 6 plugs last night and had my mechanic replace the remaining 2 today that I did not have the patience to do. It ran great all day and on my way home from work, I tromped on the gas and one of the coil packs cut out. Shortly after, the check engine light kicked on and I went to Schuck's auto parts to use the free scanner. The code I have is a freeze code of P0357 ignition coil G primary / secondary circuit malfunction.

Can anyone tell me what is the easy / primative way to test what cylender coil has failed? Will unplugging the injector wires one by one help isolate the cylender affected? The only reason I opt for injector wires is that it seems to be easier to disconnect them vs. the coil harness wires.

Thanks,
Brendan

 

Yes, you can unplug the injectors one by one to see whick cylinder is dead. I would suggest a Haynes manual for properly checking the ohms on the coil packs.

 

I found the problem... after spending $60 on a coil pack that I did not need. The wire connector on cylender #7 was hanging on by a hair. After I plugged it in all the way, it ran great and I cleared the trouble code.

It is ironic that the cylender that failed was one of the ones I had my mechanic change plugs on. All 6 that I changed were fine

 

That'll teach you to not do it yourself