P0351 code on 02 Explorer (4.0)

[lbowout]

Hi folks, my son and I replaced the valve cover gaskets on his 02 Explorer. It was running fine prior, just leaking a bit of oil from the valve cover.

There was a TON of stuff to remove to get to the valve covers and, I thought, we took special care to reconnect everything we disconnected to get to the valve covers.

Once put back together, the vehicle is idling rough and when driven gets all the way up to 5000 RPMs before shifting to higher gears. When stopping at stop signs, the vehicle will, again, idle roughly and the acceleration isn't very great either.

The only systemic code that keeps coming up is the following code: P0351 Ford - Ignition Coil 'A' Primary/Secondary Circuit

So I'm thinking on replacing the fuel filter, spark plug wires, spark plugs and ignition coil.

Is there anything else I should be considering? It seems odd to me that the vehicle ran decently prior to use taking it apart and now it doesn't. Definitely points to "mechanic error".

To be fair, I was working on my truck while my son was working on his Explorer providing oversight as needed. There were a couple of errors (P1409 & P0122) that were cleared after he researched what they were, went back under the hood and reconnected a connection that wasn't done on reassembly - doh!!! Hate when that happens.

We can't figure out the P0351 so any advice would be greatly appreciated.

Thanks.

 

[chopperb]

Seems like the coil pack or you pinched a few wires somewhere.

 

[imp]

How roughly does the engine run? You should be able to detect if only 5 cylinders are working properly, by the feel of it. A vacuum leak, if serious, might also be the culprit; maybe a combination of both. The code shown would indicate the computer is detecting incorrect current flow in the coil primary, the low-voltage side which it controls. Could you have damaged the coil pack physically? Check plug wires, as a last resort. Let us know.....imp

 

[lbowout]

Hi guys - thanks for the feedback.

When I say the engine idles "rough", I'm talking about a bit of a shake at idle (more than usual) and a pretty significant engine shake at about 1500 RPMs while driving. When we get to stop signs the rough idle continues and it feels, at times, like it might stall out - but it hasn't done so.

We never even got close to the coil pack nor did we disconnect any spark plugs during our disassembly - just disconnected the negative terminal off the battery. I did remove and reseat the spark plug wires today just to be sure one of them didn't get bumped during disassembly. Also checked and blew out each end going into the coil pack.

I also loosened then reseated & re-tightened the vacuum line on the passenger side down near the block (sorry, don't know what that's called) - we disconnected that to get the passenger side valve cover gasket off.

Engine still exhibits the same symptoms except now the code is P0355 - which gives the same "Ignition Coil 'A' Primary/Secondary Circuit" fault.

Any ideas on how to check/troubleshoot a coil pack?

 

[imp]

Hi guys - thanks for the feedback.

When I say the engine idles "rough", I'm talking about a bit of a shake at idle (more than usual) and a pretty significant engine shake at about 1500 RPMs while driving. When we get to stop signs the rough idle continues and it feels, at times, like it might stall out - but it hasn't done so.

We never even got close to the coil pack nor did we disconnect any spark plugs during our disassembly - just disconnected the negative terminal off the battery. I did remove and reseat the spark plug wires today just to be sure one of them didn't get bumped during disassembly. Also checked and blew out each end going into the coil pack.

I also loosened then reseated & re-tightened the vacuum line on the passenger side down near the block (sorry, don't know what that's called) - we disconnected that to get the passenger side valve cover gasket off.

Engine still exhibits the same symptoms except now the code is P0355 - which gives the same "Ignition Coil 'A' Primary/Secondary Circuit" fault.

Any ideas on how to check/troubleshoot a coil pack?

Just checked in my 2004 Shop manual, under ignition, all I can help with is the coil pack contains 3 coils, fires 2 spark plugs simultaneously, and troubleshooting is covered in ANOTHER MANUAL, of course, the one I didn't order, "Powertrain and Emissions and Control".

Sorry I can't give you more. But, I can tell you my own 2004 had an engine fire start due to a pack rat nesting underhood, the damn rat chewed through a plug wire completely, but the insulation still hung together, creating a spark at that point which ignited the grass and **** he had accumulated under there; this singed and melted the outside of the coil. Still worked, but I replaced it anyway. I think it was under a hundred bucks at NAPA. imp

 

[lbowout]

Well - thought I was gonna swap out a bunch of parts (spark plugs, wires, coil, fuel filter, etc...) but decided to just take it to my family mechanic and bite the bullet.

Sure enough - pinched a couple of wires or connectors going to the coil pack causing 2 cylinders to not fire properly. Save me a bunch of time under the hood and he only charged me for diagnostic fees and whatnot. Best $150 I've paid so far - I was really nervous something ELSE might be wrong if I put in $150 worth of new parts and it still didn't clear the fault.

Truck running back to normal - well, as normal as an 02 with 140k can.

 

[kevin74656]

Thanks for posting this. I had the same problem with the 1-5 coil pack on my '96, and found that the wire feeding the pack (yellow with a black stripe) had been rubbing against a vacuum hose. It must have been doing this for some time because the insulation was completely gone at the point of contact with the hose and the bare wire was exposed. I taped it up and it's now running normally.

Thanks again!!