Strange misfire

drbr0b0tnik

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I had been keeping track of my catch cans volume in one of the big catch can threads, and I had a couple of misfires occur. I figured I’d document them separately.

2015 2WD limited, 103,*** miles. Plugs are right around 12-13k miles old, auto parts store OEM motocraft, gaps checked and corrected to .031. All coils appear to be OEM originals.

Had a misfire about three weeks ago on on-ramp to freeway. It “resolved” and had no check engine light. A week later under the same circumstances, had another misfire, this time the light stayed on. Had the codes pulled, it appears the first misfire was cylinder 3, random misfire detected, and then cylinder 1.

I decided to swap the coils on cylinder 1 and 2 and attempt to recreate the misfire to see if it was the coil that was bad, given the new plugs. I have not been able to recreate the misfire though.

Any ideas?
 

LokiWolf

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Crap Motorcraft plugs. They are honestly getting worse, but should still be good with that low of miles.

How did the old plugs look. Could the coil had just been loose, and moving them you fixed that?
 
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drbr0b0tnik

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The more I’ve read about the OEM plugs, the more I wished I had just spent the extra on the Rutheniums. I may just upgrade for the hell of it and not worry about it. I haven’t gotten around to actually checking the plugs. The day I swapped the coils I just didn’t have the extra few minutes to pull the plugs. I’m off all week so I should have plenty of time to take a look at the two cylinders in question.
 

tacoduck

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Was it raining the days you hit codes? I had an issue 1 time I’m my 2017 expo in the rain. No acceleration and check engine light. I restarted the truck and never had another issue. I’ve heard under the right conditions, the truck will hit limp mode due to rain.
 

99WhiteC5Coupe

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The more I’ve read about the OEM plugs, the more I wished I had just spent the extra on the Rutheniums. I may just upgrade for the hell of it and not worry about it. I haven’t gotten around to actually checking the plugs. The day I swapped the coils I just didn’t have the extra few minutes to pull the plugs. I’m off all week so I should have plenty of time to take a look at the two cylinders in question.


GM has issued TSB’s stating that iridium-tipped spark plugs (such as the OEM Motorcraft plugs have) should not be gapped by the user, as the gap is set at manufacture.

Altering the gap can damage the iridium tip coating. The bulletins state that if the gap is out-of-spec at installation (new), the plug should not be used and another one obtained.

Perhaps when you adjusted the spark plug gaps (post #1), you damaged the plug tips?
 

LokiWolf

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GM has issued TSB’s stating that iridium-tipped spark plugs (such as the OEM Motorcraft plugs have) should not be gapped by the user, as the gap is set at manufacture.

Altering the gap can damage the iridium tip coating. The bulletins state that if the gap is out-of-spec at installation (new), the plug should not be used and another one obtained.

Perhaps when you adjusted the spark plug gaps (post #1), you damaged the plug tips?
As long as you aren't a moron and smack it with a hammer, or be rough with it, you will be just fine. I have used many Ford plugs over recent years before starting to use the NGK's. And had to adjust MANY of them. Helped a friend install Motorcrafts because he needed new and what we could find local in December, and if the case was true above we would have had to take 5 out of 6 back.

So if he takes your advice to always use OEM, he should buy several extra plugs to make sure he gets 6 properly gapped, because he can't fix the gap himself? Your advice is flawed!
 
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drbr0b0tnik

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Was it raining the days you hit codes? I had an issue 1 time I’m my 2017 expo in the rain. No acceleration and check engine light. I restarted the truck and never had another issue. I’ve heard under the right conditions, the truck will hit limp mode due to rain.

We tend to be mostly arid in the winter months, humidity has been low 20s/high teens. We did have some rain, but not the week I had my misfire.

In regards to the gapping of plugs, I mean I just just a gap tool because as Loki pointed out, I think 4-5 of my were way over gapped.

Today, I got the car to misfire under heavy acceleration. The engine light flashed as usual but then turned off. Tomorrow I’ll get the code pulled to see which one misfired.
 

Timo2824

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Have you drilled a weep hole in your intercooler? If not I'd definitely recommend it, my transit van with the 3.5 started having random check engine misfires around 70,000 miles. I drilled a weep hole at 76,000 miles and had zero CEL's through 95,000 miles when I got a new one.
 

Motorcity muscle

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Had the codes pulled, it appears the first misfire was cylinder 3, random misfire detected, and then cylinder 1.
Did you use an Auto Zone type code reader or a scan tool showing the actual running/firing? When I chased a misfire the running reader showed the problem clearly.
 
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