2021 JT CEL - Misfire cyl 3 under load only

[Smart Like Rock]

Need some advice... JT has 120K km on it (80K miles)- been a great jeep....
Had a flashing CEL and misfire a few weeks back, scanned it and it came up with a misfire on cyl 3- opened it up, the plug and injector were in bad shape, replaced, checked cyl 2, then 1 , 4,5,6 and decided to replace all plugs and injectors while I had everything off...
Now... Everything is fine, until I really put the engine under load... around 5k rpm in 5-6 the flashing CEL is back and is misfiring... but only under load... after you throttle off, it goes away, and misfire stops...

New CEL says its cyl 3... again... coils look fine...

Anyone have any pointers?

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[Advntrbound]

In, to see what others may offer. I've developed a bad misfire with obvious loss of power and stuttering when I'm trying to get to speed to merge onto the highway. If I'm careful, all will be well, but if I hammer down the misfires happen.
I just received new plugs from RockAuto and plan on putting them in next week after a mini vacation. Hopefully that fixes the issue.

Edit to add. I have to pullover and restart the jeep for it to go away. I did reset my tire size with j-scan prior to this starting. After plugs, if it happens then I'll have the dealer re-flash everything back to factory.

 

[Smart Like Rock]

In, to see what others may offer. I've developed a bad misfire with obvious loss of power and stuttering when I'm trying to get to speed to merge onto the highway. If I'm careful, all will be well, but if I hammer down the misfires happen.
I just received new plugs from RockAuto and plan on putting them in next week after a mini vacation. Hopefully that fixes the issue.

Edit to add. I have to pullover and restart the jeep for it to go away. I did reset my tire size with j-scan prior to this starting. After plugs, if it happens then I'll have the dealer re-flash everything back to factory.

Same as my symptoms... everything is fine until you punch it...
Replaced all plugs and injectors, 1 fouled plug and 1 bad injector, but replaced them all as I was in there already...
Didn't solve the issue...

 

[Advntrbound]

Same as my symptoms... everything is fine until you punch it...
Replaced all plugs and injectors, 1 fouled plug and 1 bad injector, but replaced them all as I was in there already...
Didn't solve the issue...

Do happen to have a 6 speed manual? I just had the clutch replaced last month and I assume some software updates as well. Wondering if the update might be the cause.

 

[Smart Like Rock]

Do happen to have a 6 speed manual? I just had the clutch replaced last month and I assume some software updates as well. Wondering if the update might be the cause.

Auto 8 sp...
From what I see, and read... misfires are the start of something much bigger....

 

[Volt0]

Coolant levels holding good?

 

[Smart Like Rock]

Coolant levels holding good?

Yep.. haven't had to add anything...ever....

 

[Volt0]

And for that bad injector, what was bad about it? In other words, do you have contamination in your fuel lines?

Am asking b/c something took out that plug & injector.

 

[Smart Like Rock]

And for that bad injector, what was bad about it? In other words, do you have contamination in your fuel lines?

Am asking b/c something took out that plug & injector.

I have over 100k km on it, gas quality sucks here, it's age and probably bad gas over time... I'd imagine...

 

[sdeetch]

New to Gladiators. Just bought one a month ago. It looks like these engines have coil packs. If that's the case, could it be a coil packs? That would explain the misfire and potentially the wear on the plug. Used to happen on my Toyota after 80k to 100k miles

 

[Hootbro]

You have already done spark plugs and like mentioned, would look at coils. Since it is the right side that is accessible, you could swap 1 & 3 coil to see if it travels. If it does not travel, then I think you are going to need a higher end scan tool that can monitor real time ignition and cam advancement to see what commanded vs. actual cam degree timing is going on. If there is a mismatch, probably looking at cam, timing chain and/or cam phaser issues. I would not lean on a VVT solenoid since it is not the whole right 1, 3, 7 cylinder bank giving a misfire.

While not a fix, I would recommend pulling and having an oil analysis done to see what the iron wear numbers are doing. If excessive, you know it is going to be mechanical on that right head of some sort.

 

[Gregj]

Pull the right side valve cover and look at the rocker arms and lifters, this is a known, common failure point in the 3.6. Misfire codes are usually the first sign. Hope you caught it early and it is a simple fix, just replacing the rocker arm. Waiting can end up destroying the cam and eventually the whole engine.
Gregj

 

[Smart Like Rock]

New to Gladiators. Just bought one a month ago. It looks like these engines have coil packs. If that's the case, could it be a coil packs? That would explain the misfire and potentially the wear on the plug. Used to happen on my Toyota after 80k to 100k miles

ya I think I'm gonna swap them all out... see where that leads..

 

[sdeetch]

Look at what Hootbro said. You can swap coil packs easily. If the coil packs is bad, it will throw the same code, but in a different cylinder. Much better than cherry picking them all.

 

[Smart Like Rock]

Pull the right side valve cover and look at the rocker arms and lifters, this is a known, common failure point in the 3.6. Misfire codes are usually the first sign. Hope you caught it early and it is a simple fix, just replacing the rocker arm. Waiting can end up destroying the cam and eventually the whole engine.
Gregj

Appreciate the advice, we installed new coils and got the P0300 code again, this time 4th cyl...
seems like it is the 2-4-6 bank that is giving the issue, will pull the valve cover and take a look at the rockers and lifters....

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