Hi all. I bought an 2012 e350 last week with enough miles to be out of the drivetrain warranty. As I was driving it home, it started running really rough at idle and at 60mph+ it started shaking like I was doing 20mph on a washboard road. The CEL came on, so I used torque to retrieve the codes. I got P0351 - Ignition Coil "A" Primary/Secondary Circuit Malfunction

I found invoices were a previous mechanic worked on it. He said that he replaced the coil pack, which cleared the code, and then the spark plug at a later date because the code and misfire had returned. He said that the code would continue to return because the internal valve seals were leaking and saturating the spark plug.

In hopes that the oil was coming from the valve cover, I pulled the spark plug to see where the oil was coming from. The coil and boot were clean and dry. Here is a picture of the plug. It should have about 250 miles on it. It didn't seem to be covered in oil. The paper towel shows how much I cleaned off of the tip of it. I put it back in and the code cleared. My thoughts of a valve cover gasket have been shattered. However, it still ran like a turn and the CEL came back.

Today, I am going to work through the diagnostics in this post in hopes of solving it.

I was wondering if anyone had any thoughts about the "valve seal leak" and its ability to cause this issue. Thanks!

 

Pulled and tested CPS. Its resistance was at about 380, so it's good. The misfire is consistent and at both low and high temps, so I didn't need to heat and test it. There is voltage at its connector. Time to test the coil pack....

 

not a major valve seal leak.. based on that one spark plug....

do not depend on the code and the number on the cylinder to be accurate...

pull all the spark plugs... that is the correct way...

the spark plugs will tell the cylinder that is not correct.

my opinion.

 

Look carefully at the seal on the low voltage connection to the coil. I had one that was cracked and it allowed water into the plug which threw the same code because the current was shorting through the water and not firing the coil. Good luck!

 

The code says primary or secondary circuit malfunction. It would not be the spark plug in that case. Look for a coil problem or wiring to the coil. Also Chuck is correct. I have a Snap-on verus and doing a cylinder contribution test on early Fords show a problem with a cylinder but it may not be the one the scanner says it is. I had a lincoln that I had to physically pull coil wires to determine which cylinder was misfiring.Verus said cyl 2 and it was cyl 8. I've seen this a couple of times. E350?? what a pain to work on!

 

A valve seal leak would cause oil consumption, but not normally a miss.

A failure of a valve to seal against the valve seat can cause a misfire like symptom, depending on how bad it is.

 

But it won't throw a coil circuit code.