Vehicle: 2016 Ford Explorer 3.5L non-turbo, 110,000 miles
Problem: Extremely rare but severe misfire. Codes P0300, P0302, P0306.
Our patient today has been exhibiting a severe misfire 0.1% of the time. I can drive it to town (10 miles), around town, to school (14 miles) for weeks without any issue, purrs like a kitten. It only happens, as far as I have found, under 2 conditions: 1) full throttle acceleration up to at least 50mph, and 2A) at interstate speeds using cruise control, triggered by downhill deceleration/coasting, or 2B) going up a big hill. Those conditions seem to me to be at odds with each other. It will stumble, AC turns off, and then 5-10 seconds later it is running perfect again. The flashing CEL goes out before I can even really slow down or pull off the road.
Fuel injection system has been flushed and serviced. New coil packs (Denso) and spark plugs (NGK) installed by me, no change.
I took it to the "experts" (Ford dealership) hoping they would run some serious diagnostics on it and find an answer. Nope, they blame my "junk" non-Motorcraft parts and want to replace them all as the first step. I explain that it has occurred with MC parts, new parts, swapped parts, doesn't matter. They are unfazed. I leave. It is always the same 2 cylinders, #2 and #6, which are on different banks and have separate catalytic converters.
Any ideas? I don't want to parts-cannon this thing if I can avoid it.
Did you get the Ford-specific DTCs? If not, do you have access to a scanner that can access them? I'm not saying they will magically solve your problem, but they might offer more direction than generic OBD2 misfire codes.
I had a weird but similar problem in a '14 dodge, but only one cylinder. It was the coil.
In reply to O2Pilot:
I got nothing from them. I don't have a better scanner. That is what I was willing to pay them for, until they just wanted $800 to replace new parts that are working fine.
I did find the Ford HD: misfire detection monitor chart, and I'm not sure they got very far into it. Only had it for 2 hours total.
checking stuff out on i Aint Testing Nothing found a couple hits of exact issue, logging misfire at WOT and also under neutral/decel, on different banks, even after replacing plugs and coils and/or playing musical components to see if the misfire moved somewhere else.
Fix was to perform a misfire monitor neutral profile correction.
I note that in your case and others I had seen, the common component was that the cylinders in question were 360 out in the firing order. 142536. 2 and 6 happen at the same point in the crank sensor signal. Could there be damage to the crank trigger wheel? Maybe. Crank sensor going bad? Maybe. Crank trigger wheel got changed/moved and you are now finding out that you should have done the relearn after doing that? Usually the case, per the iATN cases I quickly glanced over...
In reply to Pete. (l33t FS) :
That is awesome. Thank you! As far as I know, the crank sensor/ trigger wheel has never been touched, so I will look at that. Thanks again
wae
PowerDork
6/9/23 10:33 a.m.
I *think* that if you have FORscan, it will allow you to scope the crank signal from the OBDII port.
if possible, I would just do the relearn and be done with it, if there are no other issues.
FORScan tool inbound, I'll update next week. Really appreciate the help!
btw, I googled "i Ain't Testing Nothing", cause it seems like my people, but only got hits for music I ain't never heard of.
Maybe with this I can disable the damn "double honk when you step away with the engine on" that makes me want to punch somebody.
llysgennad said:
FORScan tool inbound, I'll update next week. Really appreciate the help!
btw, I googled "i Ain't Testing Nothing", cause it seems like my people, but only got hits for music I ain't never heard of.
It's a joke name for the iATN. Kind of like "Spoiled Children Crashing Automobiles"
In reply to Pete. (l33t FS) :
Yeah, I figured that out. Just kinda hoping it was real...
Pete. (l33t FS) said:
if possible, I would just do the relearn and be done with it, if there are no other issues.
Pete, you are the man! I owe you.
Did the relearn last week, just drove 700 miles through the Ozarks over the weekend. Not a single hiccup (or CEL).
It's going to take me a while to adjust to 3 minute software fixes for vehicles. Not my natural thought process.
In reply to llysgennad :
Glad to hear that it's sorted.
The key is that the engine was never misfiring. It was falsely detecting a misfire, so it would cut fuel to those cylinders. Sort of the difference between a "crash" and "controlled flight into terrain" 
