GEN 2 Need help diagnosing misfire codes under certain conditions.

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sfemti33

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I have a 2018 with misfire conditions that I need help running down. I'm only asking now as it's Sunday and the shop is closed so I'm seeing if anyone has other thoughts.

Last week I was cruising on freeway about 75mph when I mashed the peddle to pass traffic. Got up to 90 and my app said there was a misfire on cylinder 5 only (p0305) when I pulled code later. No rough idle rest of trip home but I didn't drive hard and used surface streets. Took it to shop next day and they said several of my plugs were loose so they tightened them, drove it, and said I was good to go.

Last several days I've been able to replicate something similar under same conditions. I was driving last night similarly and felt a shudder/ pop pop pop but no code so hoped it was a one off.

Today same type of driving conditions, shudder/pop pop pop but this time CEL started flashing and I pulled off freeway and turned to home (only a mile away). The CEL turned to solid and no rough idle or anything as I drove <50mph home. Codes this time were p0301, p0305, and p0300 for cylinders 1 and 5 misfiring, and random/multiple misfiring.

It only happens under those conditions and my buddy thinks it's bad gas. I'm worried it's something much worse.

Thoughts?
 
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sfemti33

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What have you tested so far?
I'm not a big wrencher myself so not much? I changed all 6 plugs about 14,000 miles ago. The shop said they tested plugs and wires and all seemed well after that first issue. I've had valve covers replaced in the last 2 years, one having to be redone due to new leak. I don't know how to test if it's bad gas.

I service all fluids at normal intervals. This did just start happening after it was in the shop to have starter, flex plate, and drives shaft replaced. I was at about 1/2 of gas while it was in the shop for 2 weeks in Utah climate. I then filled up at a 7/11 I often use, but not exclusively. The first instance happened shortly thereafter and I am at 2/3 tank of gas now.

I believe cylinders 1 and 5 are on opposite sides of the engine so I have some thoughts on what it isn't, but again I'm not a mechanic.
 

smurfslayer

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hmm... that’s eerily similar to what happened to my wife’s Lincoln not long after buying in 2021. Stealership had it for I think 3 weeks and after week 1, were talking to Ford Engineering. They were able to replicate the problem and eventually, we got a whole new set of injectors, fuel rails as I recall. along the way, they did compression, load balance tests, a bunch of acronym soup - money shot appeared to be they found fuel in cylinders after several tests. No coils or plugs implicated...

really, same situation, although it was abnormally cold, just driving along after a mild acceleration and MIL comes on.
 
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sfemti33

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hmm... that’s eerily similar to what happened to my wife’s Lincoln not long after buying in 2021. Stealership had it for I think 3 weeks and after week 1, were talking to Ford Engineering. They were able to replicate the problem and eventually, we got a whole new set of injectors, fuel rails as I recall. along the way, they did compression, load balance tests, a bunch of acronym soup - money shot appeared to be they found fuel in cylinders after several tests. No coils or plugs implicated...

really, same situation, although it was abnormally cold, just driving along after a mild acceleration and MIL comes on.
It's not abnormally cold here. Truck is sufficiently warmed up. Does not do it under light or even moderate acceleration and no rough idle or really anything different after it happens.

Also just checked and coolant is at max line after it was flushed a year ago, and no obvious oil around valve covers.
 

smurfslayer

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It's not abnormally cold here. Truck is sufficiently warmed up. Does not do it under light or even moderate acceleration and no rough idle or really anything different after it happens.

Also just checked and coolant is at max line after it was flushed a year ago, and no obvious oil around valve covers.
Lincoln didn’t idle or run rough, had plenty of power.
 

Trailmaker

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Following.

I too have a misfire. It’s on 5&6. New coils and plugs. Runs better when outside temp is below 55F. Almost no issues when it is colder then 40 outside. 151k on the OD
 
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