2016 cylinder misfire issue

[beanford]

Hey, looking for some advice on my 2016 ford expedition 3.5L 135k miles.

Had CEL first started under heavy load (60mph, diving uphill, etc) pulled codes and got misfire cylinder 6 and a few random misfire codes. So I replaced the plugs and now I’m only getting a cylinder 3 misfire.

I replace the cylinder 3 coil Make sure the coil was seated on 3 and still getting a misfire without CEL and a P303 code.

So I took it to a local chain shop for a diagnostic. They said it was probably a fuel injector. They however were not confident in that fact so I decided to take it to a Ford dealer.

They old me I replaced the wrong coil, I don’t think I did based on the attached picture for cylinder location, but they said they swapped it to confirm and that it is not a coil issue but that it has a bad fuel injector.

They replaced the bad fuel injector (I asked them to replace all 3 since they had the manifold off and their tech only replaced the one which was frustrating)

Tonight we are driving up a canyon and start feeling misfiring again. Not CEL and it has been 3 days since we picked it up and have not had a misfire until tonight.

I don’t trust the dealer at this point anyone else have any suggestions where I should look next to solve this?

 

[JasonH]

Check the plug gap. You can swap coils to see if the issue follows a specific coil. Cylinder 3 is passenger side closest to the firewall.

 

[beanford]

Check the plug gap. You can swap coils to see if the issue follows a specific coil. Cylinder 3 is passenger side closest to the firewall.

I swapped coils, the shop swapped coils and the dealer swapped coils. It stayed on cylinder 3 each time.

Also I have not checked the plug gap but 6 new plugs were installed that come pre gapped from what I understand.

 

[tacoduck]

Ugh. Subbed for outcome.

 

[gimmesomecoffee]

.

 

[drbr0b0tnik]

What brand of plug? Cause motorcraft are garbage (and their pregap is as garbage as they are). I replaced mine with NGK Ruthenium gapped at .028 and I've not experienced a single misfire since.

Edit: I forgot that I also ordered mine one step colder.

 

[JasonH]

I swapped coils, the shop swapped coils and the dealer swapped coils. It stayed on cylinder 3 each time.

Also I have not checked the plug gap but 6 new plugs were installed that come pre gapped from what I understand.

Check the plug gap and check the insulator for damage. Easiest thing is to swap the plugs between cylinders after checking and see if the issue follows the plug. Sounds like this was done for the coil but not the plug itself.

 

[beanford]

What brand of plug? Cause motorcraft are garbage (and their pregap is as garbage as they are). I replaced mine with NGK Ruthenium gapped at .028 and I've not experienced a single misfire since.

Edit: I forgot that I also ordered mine one step colder.

I replaced them with NKG but I did not check the gap since they were supposed to be pre gapped. I will check the gap and see where they come in.

 

[beanford]

Check the plug gap and check the insulator for damage. Easiest thing is to swap the plugs between cylinders after checking and see if the issue follows the plug. Sounds like this was done for the coil but not the plug itself.

You are correct I swapped the coils but not the plugs.

 

[beanford]

Well an interesting development. I know the Expedition was misfiring on Saturday driving up the canyon took it to the auto parts store today and had them pull codes and there was not a code to pull. Not sure what to make of that.