Misfire Nightmare

[lingerfelt2016]

This is gonna be a long one so buckle up!

I replaced the engine in my 4.0 about 2 summers ago. Ever since then I've been having the biggest hassle with my Explorer. It started experiencing a misfire issue September of 2015. I tried replacing the coils and spark plugs plus all the wires. Then it got even worse. It started reading codes for all cylinders misfiring, and was driving worse than ever. After taking it to a shop finally to see if they could find anything, they replaced a spark plug and it was fine for a few days. Then it started right back up with the rough driving and misfire. So I took it back and they replaced the fuel injector. It ran fine for again a few days and now it's driving worse than ever. The check engine light is flashing constantly. The mechanic at the shop I took it to showed me a section of the wiring harness that was apparently melted by resting on the exhaust manifold, and said the only hope in rescuing this car without doing an entire wiring harness replacement would be to seperate the individual burned wires and wrap them with electrical tape. I just tried seperating them and so far nothing has changed. Is there any hope in this? Or am I going to seriously have to consider replacing the wiring harness in order to solve this issue? Any input is appreciated. Thanks for reading!!

 

[Explorer_PL]

When I had my car at the dealer for some diagnostic work, they also gave me a very detailed graph and statistic for each cylinder showing how many misfires took place on each cylinder. Some would show just few which is normal, but 2 or 3 was showing numerous ones, like 30 and up. Interestingly, the CEL was not on. Maybe it would be beneficial to have a test run to pin point a cylinder, and then concentrate on the wires, and maybe injector and spark plug for that cylinder. And use OEM parts only, don't bother with aftermarket.

 

[Tech By Trade]

Fuel filters like to starve the rail to the injectors on these things when they plug causing a missfire on the 2 end cylinders.

 

[SteveOReno]

This is gonna be a long one so buckle up!

I replaced the engine in my 4.0 about 2 summers ago. Ever since then I've been having the biggest hassle with my Explorer. It started experiencing a misfire issue September of 2015. I tried replacing the coils and spark plugs plus all the wires. Then it got even worse. It started reading codes for all cylinders misfiring, and was driving worse than ever. After taking it to a shop finally to see if they could find anything, they replaced a spark plug and it was fine for a few days. Then it started right back up with the rough driving and misfire. So I took it back and they replaced the fuel injector. It ran fine for again a few days and now it's driving worse than ever. The check engine light is flashing constantly. The mechanic at the shop I took it to showed me a section of the wiring harness that was apparently melted by resting on the exhaust manifold, and said the only hope in rescuing this car without doing an entire wiring harness replacement would be to seperate the individual burned wires and wrap them with electrical tape. I just tried seperating them and so far nothing has changed. Is there any hope in this? Or am I going to seriously have to consider replacing the wiring harness in order to solve this issue? Any input is appreciated. Thanks for reading!!

I also have a misfire problem, but mine is only one cylinder. Disconnecting the battery for a while resets the computer and fixes the problem for a while, which seems to be your situation too. I am thinking about installing a 200A relay on the battery feed (not the starter feed) so I can disconnect the battery every time I park. If it runs great for a while each time why not?

 

[yoster]

Fuel filters like to starve the rail to the injectors on these things when they plug causing a missfire on the 2 end cylinders.

This. My 4.6L was missing (almost thought the transmission was going out or something) - replaced the fuel filter and wala - problem solved.