u/NotoriousCFR

I'm having the most aggravating issue with my truck and I'm hoping someone here has some insight. It has an intermittent, seemingly random misfire. It happens mostly at highway speeds, under heavy acceleration. My fuel economy is also lower than it should be/was in the past, which may or may not be related. 130k miles on the truck.

First, I did the obvious, had the spark plugs replaced (they were due anyway). Made sure to use Motorcrafts. It started misfiring again a couple days later. Eventually, it threw a CEL code, the shop read it and said it was a cylinder 3 misfire. they swapped coil packs between 3 and 1 to see if the code would move over.

Then, the truck ran perfectly for a couple weeks. Fast, slow, pedal to the metal, didn't matter, drove like it was brand new. But eventually, it started misfiring again, more and more persistently (no code though). I brought it back to the shop, they drove it around for 3 days and said they couldn't replicate the issue. They shrugged and gave the truck back to me - no work done, no cost.

After a few more weeks it finally misfired bad enough to throw another CEL code - P0300, "random misfire". I had a hellish work schedule stint and didn't have time to get to the shop, but it "self-corrected" and started driving fine on its own anyway.

A couple weeks later, it started misfiring again- same thing, more aggressively and more persistently for a few days, and it finally threw a code saying misfire on cylinder 2. Remember that the last cylinder-specific code was on 3. I brought it the mechanic immediately after the code came up this time.

It is now at the shop again and they once again are unable to replicate the issue. The tech says the spark plugs look fine, and all 6 coils tested fine as well. They've been driving it up and down the highway for 2 days trying to get it to do something and it's running perfectly fine.

I've ruled out the possibility of bad gas (filled up at many stations, no correlation). Engine air filter was just replaced 2000 miles ago. I have not done the 24E12 PCM recall but it doesn't seem like that would matter.

What I'm wondering is:

• Are there any other components that my mechanic could/should be inspecting or testing regardless of whether or not they're able to actually replicate the misfire?

• If they give up and just toss the keys back to me again, is there any DIY diagnostic stuff I could do to try and narrow down the problem?

• Would I have better luck going to a Ford dealer? I fucking hate dealerships but I know that they may have more advanced scan tools that can tell them more.

Really hoping to get to the bottom of this sooner rather than later. Thanks in advance to anyone who has relevant advice 🙏