Code 301 misfire issue

[AWD EXPY]

Cylinder #1 has an ongoing, intermittent, rough running, misfire about 85% of the time. It started a couple days ago. 190K miles on this 97 with a 5.4L. I had to change the alternator last week. I've had it about 6 months.

The plug well was dry and the boot popped when I pulled it off. It seemed to be sealed ok. I swapped the plug with an ngk platinum (recommended). It didn't stop misfiring. The old plug seemed ok.

Today I did an ohm check on the COP. The primary tested at 1.4 ohms, and the secondary tested at close to 5.5K ohms. The injector tested at 15.5 ohms.

Is the primary coil resistance too high for the COP to make decent spark?

Maybe a clogged injector?

 

[stamp11127]

Found this on the internet so it must be true.....bonjour


Peak Current: 8.5
Voltage: 35000
Primary Voltage: 14.2
Brand: Motorcraft
Maximum Voltage: 35000
Primary Ohm Resistance: 0.5
Secondary Ohm Resistance: 5500
Coil Color: Black

With .5 ohm on the primary the current will be 24 amps. With the 1.5 ohms the current changes to 8 amps which may give a weak spark. Move the coil to another cylinder and see if the problem moves with it.

 

[AWD EXPY]

Thanks. I'll do that in the morn, then get a new code read.

 

[AWD EXPY]

Did that...still ran rough, but no code. (not enough cycles) I had the battery discon for a bit. I bought another cop and installed anyway, and it took care of the misfire problem.

Thanks for the response.

 

[AWD EXPY]

An update...when I first checked resistance with the old coil still installed, I got 1.8 ohms. A second check showed .9 ohms. The unit I swapped out, measured .9 ohms. The new one I installed measured .9 ohms. So no pinpoint conclusion there.

Still running mostly alright, but some other cops could stand to be changed out.