Check engine light after hard braking

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duderz7

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Last night I had to do a full pressure stand on the brake hard stop to avoid an accident. It was scary considering I just got the jeep back together. I got back up to about 65 maybe a minute later and felt a hiccup, almost like I hit a bump, then another minute later the whole Jeep is shaking and CEL is flashing. So I let off the throttle and started looking for a safe place to get of the highway and suddenly everything smoothed out and light went out. Ran fine and started and ran fine later after cooling down and this morning too. Thoughts?

Other things to note.
It was about 30°f
I had just left the house so Jeep was far from warm.
The half tank of gas has been in there since summer.

On a good note it inspired me to check some basic things so I cleaned pcv, throttle body, and IAC. And while I was there reloomed some crusty wire looms.
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lfhoward

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That is interesting! Considering the old gas, it could have been a coincidence. Or, maybe all your gas sloshed to the front of the tank and your fuel pump took up air for a second, leading to a misfire. Can you read the codes, or pending codes as the case may be?
 

duderz7

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That is interesting! Considering the old gas, it could have been a coincidence. Or, maybe all your gas sloshed to the front of the tank and your fuel pump took up air for a second, leading to a misfire. Can you read the codes, or pending codes as the case may be?
I was kinda thinking that way on the gas. Checked for codes with a reader and the key trick and got nerthin, no codes at all.
 

duderz7

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CEL came back tonight with a rough idle. Me thinks the hard braking moment was coincidental. I'll check codes tomorrow, it's dark and cold out there and I'm afraid of both.
 

duderz7

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P0304, I'll do some coil swapping and inspection when the opportunity arises.
 

duderz7

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Here are my findings.
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never seen a plug turn red before? I pulled another and also found it to be red. However I do believe I have a leaking coil boot. Somehow picture did of that didn't save. I swapped coil 4 with 6 and we'll see is cod follows. On a side note my plugs were barely snug. As soon as I put very little reverse pressure on them they began to spin. Not sure, but I think the guy that put the plugs in my have not properly tightened them. I'd ask him, but talking to yourself is weird. Ngk coils? All or one?
 

LibertyTC

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Wow red hot ! Get some new factory plugs in there. Ngk ZFR6F-11G gap them at .040 inch
 

derekj

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I have seen lots of plugs discolored like that before - some of it is from the additives that get put in gasoline.
 

duderz7

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I have seen lots of plugs discolored like that before - some of it is from the additives that get put in gasoline.
That's what I read. Pretty sure that's not my problem. I'm certain it's the coil. I'll get a picture soon.
 

sota

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given your loose plug findings and their coloring, I'd personally do the following: assuming the tank is below 1/4 (fuel light is on)...
new plugs
fresh tank of gas
bottle of seafoam
run that until dry, or until another misfire event happens.
then move on to other steps (coils)

if you have more than 1/4 tank, i'd put those plugs back in, run 'em until the tank is empty, then do the above. no point in messing up fresh plugs. if you have the ability to drain the tank, I would.
 

duderz7

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given your loose plug findings and their coloring, I'd personally do the following: assuming the tank is below 1/4 (fuel light is on)...
new plugs
fresh tank of gas
bottle of seafoam
run that until dry, or until another misfire event happens.
then move on to other steps (coils)

if you have more than 1/4 tank, i'd put those plugs back in, run 'em until the tank is empty, then do the above. no point in messing up fresh plugs. if you have the ability to drain the tank, I would.
Thanks for the advice. I did put berrymans (similar to seafoam) brand stuff in the 1/4 tank I had then filled up. I did some searching and found that the discoloration on the plug is not a concern according to NGK. Plugs are actually pretty young. I don't have the ability to check real time misfire, but I'm fairly certain there's a small hole in the coil boot where they glue the 2 parts together. The misfire is inconsistent, I think I'm getting partial spark most of the time. Swapped coils and cleared codes, waiting for it to return to confirm the trouble coil. I'm leaning toward the Standard brand coils I've seen mentioned here, but may pony up for the Mopar one's. Surprisingly found a fair number of negative reviews on the NGK coils.
 

duderz7

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Picked up a "Standard" brand coil and popped it in this morning. They only had one in stock so I'll get the other 5 in later. Never did get another CEL, but didn’t feel good about driving it while it was idling rough. I haven't started it up since I've nowhere to go today. Pretty dang sure this is the solution, I'll report back if not.
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Here's the old coil. I can't explain the liquid there, but the second picture shows the whole where I believe spark was escaping.
 

sota

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I don't see any burn marks, and if it were sparking through there it'd DEFINITELY leave a tell tail sign.
you could try fishing some thin wire through that hole and probing it to see where it goes, if anywhere.
 

duderz7

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I don't see any burn marks, and if it were sparking through there it'd DEFINITELY leave a tell tail sign.
you could try fishing some thin wire through that hole and probing it to see where it goes, if anywhere.
When I lifted it off the plug while running I could see it arcing out the side. I think the liquid in the one picture might be the epoxy (white stuff) melting and maybe preventing a burn mark, I'll look at it closer. It's definitely running smoother with the new coil.
 
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