2017 Expedition - Jerky acceleration, misfires (P304, P300, P305)

[Cody Hall]

Attached are some pictures.

 

[Calman2k]

Attached are some pictures.

Hey Cody, I hope I can help, my '16 XLT was doing the same thing. It was a cracked plug. The crack was so small you couldn't see it without really looking at it. So I had the dealer put all new plugs in when I had the 100k maintenance done. Less than 5k miles later I was getting the same behavior and a misfire on 3. Dealer changed the plug, it was cracked (a brand new plug) fast forward another 15k miles and it did it again. But no codes. I found a really good mechanic and he said Fords are notorious for having engine issues and trying to correct for it without throwing a code. So he dug out all six plugs and found cracks in two of them, I think it was on 2 and 5. So he put all new ones in and it fixed the issue and my mileage went back up. Apparently, the engine will misfire enough times the engine will basically shut down that cylinder, which is why your mileage drops. And these engines run at such high pressures, just knocking a plug against the block accidentally can be enough to cause a crack later on. Out of the 6 the dealer put in my car, 3 ended up cracked. Call it dealer idiocy, touchy parts or whatever, it's an issue that wasn't too hard to fix on my truck.

 

[klimalaska]

Not sure if you tried this, but my brother bought a 2015 w/ the same engine and issue. Drove fine and only had the misfire issues when passing on the highway or under heavy load. Turns out that most of the plugs were eroded to a point unbelievable that the truck would even run.

We replaced plugs and wires and he’s not had an issue since. Don’t think the plugs were ever done (liked to be OEM) and it was at about 190,000 miles.

 

[drbr0b0tnik]

As has been mentioned, I would re-inspect the plugs. My 2015 had similar symptoms, and I replaced all the plugs once. The issue was gone for about 13k miles and it was back. All the plugs were already chewed up. These EBs will eat regular plugs up for breakfast. I upgraded to the NGK ruthenium plugs, one step colder, gapped at .028" (per recommendation by this forum) and I haven't had a single misfire since. I'm currently going on about 20k on the plugs right now. 113k on the truck.

 

[GaryH]

Coils can go bad before 100k. I had three go bad on mine. First one around 60k , second one around 70k. When the 3rd one went bad at 90k, I replaced them all along with some new spark plugs. Had the some of the same codes as you did, P305, P303, P308.

 

[Cody Hall]

Appreciate the comments. It sounds like I need to check the plugs and coils again. I guess I think it unlikely to be the spark plug or coil on cylinder 4 where the issue is occurring (P304 code), since I just replaced all the plugs and swapped cylinder 4 and 5 coils and the issue was the same on #4. But as mentioned, there is a chance I damaged #4 plug putting it in. Or maybe I need to gap them down to .028" as recommended, as I left the motorcraft plugs pre-gapped around .033".

Question - Is it possible the connecting ignition coil wires on coil #4 are damaged or bad? I did place some dielectric grease on the connectors when I reattached the ignition coil wires but didn't notice any obvious damage. Has anyone had issues with the wires? I assume these wires run directly from the PCM?

 

[S20Workstation4]

The random misfire issue is now a mystery for me. The carbon build-up on the valves would've sure caused problems in the future, if not already partially affecting the misfires (along with whatever else is causing the misfires). You may see an increase in MPG after cleaning those valves too.

If you happen to have pictures of the valves, I would like to see them.

I'll get back to you on possible causes, I'll have do some research because I'm out of ideas...


- Joseph

 

[Ellison Brown III]

Damn… I was happy for you. For a few seconds before I read the update. Dang!!!

 

[Utah Driver]

1. Never change the gap on platinum plugs.
2. If the computer says there is a problem on number 4, then there is a problem on number 4.
3. You can't manually clean valves on the engine.
4. Never use dielectric grease on any wire that goes to a PCM.
5. Better take this to an experienced professional.

 

[Cluster333]

Not sure if you have resolved your issue but saw this in a different Forum.
I have a 2017 and I changed the plugs after I had misfire at 79000 miles the day after I bought the Expedition. My misfires returned at 110000 #5 and #6 cylinder. I bought new coils and went with the performance gt cold spark plugs 12405-35t. All misfires resolved. I also have a catch can and boy does it catch the crap. Maybe checkout the turbo and intercooler for excessive oil.

Well, the misfire issue I had described earlier that I was working through with both MPT and ZFG has finally been fixed. I decided to back track from when I did my cam phaser repairs, and turns out when reinstalling the intake manifold, I cranked down one of the bolts too far and it poked a small hole in the valve cover, close to the intake tract for cylinder 4. Cylinder 4 was misfiring only under the most extreme and harsh conditions. I think what was happening is cylinder 4 was sucking oil from the PCV system built into the valve cover and when I was getting those crispy shifts with ZFG and MPT at WOT, it was disturbing things enough to make it misfire. Replaced the driver side valve cover and all misfiring is gone on all tunes no matter what.