New engine misfire (solved)

[Gladiator_3.6]

Hello,

Of course our 2020 gladiator ended up with the dreaded cylinder 3 misfire after 50k miles and of course warranty weaseled their way out of doing anything about it. We went out and bought a whole brand new long block heads and timing attached from the dealer and did the change ourselves, as we've changed plenty of motors in the passed. Upon first start of the new motor it now has a cylinder 5 misfire, we haven't looked into it to hard yet but being brand new factory plugs and the coil hadn't had a problem before what are yalls thoughts?

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[Gvsukids]

Hello,

Of course our 2020 gladiator ended up with the dreaded cylinder 3 misfire after 50k miles and of course warranty weaseled their way out of doing anything about it. We went out and bought a whole brand new long block heads and timing attached from the dealer and did the change ourselves, as we've changed plenty of motors in the passed. Upon first start of the new motor it now has a cylinder 5 misfire, we haven't looked into it to hard yet but being brand new factory plugs and the coil hadn't had a problem before what are yalls thoughts?

Does that work include valves and lifters? My misfire fix needed new tappets on the passenger side.

 

[LouisvEarlleJT]

I'd triple check every connection.

Can you share more of how it wasn't covered under the powertrain warranty? That's a very concerning thing to hear.

 

[ShadowsPapa]

Hello,

Of course our 2020 gladiator ended up with the dreaded cylinder 3 misfire after 50k miles and of course warranty weaseled their way out of doing anything about it. We went out and bought a whole brand new long block heads and timing attached from the dealer and did the change ourselves, as we've changed plenty of motors in the passed. Upon first start of the new motor it now has a cylinder 5 misfire, we haven't looked into it to hard yet but being brand new factory plugs and the coil hadn't had a problem before what are yalls thoughts?

If you've really "changed plenty of motors" then you know that a misfire can be dozens of things!
It can be that the PCM hasn't learned the CCDIFF, it can be ignition-related, like plugs and coil packs or a connection, or it could be fuel related - injector issues and so on.

You need to get a decent code reader and catch it in the act of misfiring. Not all misfires will set the MIL - at times, it will be recorded but you'll see in the logs of something like AlfaOBD where it says "MIL not requested" where it saw a problem, but figured it was transient or didn't really have a solid answer as to code to set.

Otherwise, what's going to happen with a question like you posed, which is the same as "doctor, my arm hurts, what's wrong" - is people coming in and tossing mud at the wall to see what sticks.
Until you post all of the details, we'll be playing 20 questions.
Exactly under what circumstances do you get the misfire? Cold start? Hot/warm start?
Under load? Idling?
What are you using to determine cylinder 5 misfire? A cheap code reader?
A decent app or reader will give you more details - even suggesting whether it's ignition or fuel related.
Or, maybe you made a mistake somewhere in putting the "new motor" in - so start by triple-checking your own work.............
That's where I start if I do something major and run into a hitch - what changed? Oh, me - I worked on it. OK, I'll start there - maybe I missed something, didn't get a connection connected properly, etc.

Otherwise, we are all guessing - cylinder 5 misfire - could be fuel, could be ignition, could be something you did or didn't do, could be the PCM needs to learn - you didn't say at all how many miles you put on since the misfire!
Did it misfire right out of the gate?

 

[Gladiator_3.6]

Does that work include valves and lifters? My misfire fix needed new tappets on the passenger side.

New heads and everything besides the valve cover and timing cover

 

[Gladiator_3.6]

If you've really "changed plenty of motors" then you know that a misfire can be dozens of things!
It can be that the PCM hasn't learned the CCDIFF, it can be ignition-related, like plugs and coil packs or a connection, or it could be fuel related - injector issues and so on.

You need to get a decent code reader and catch it in the act of misfiring. Not all misfires will set the MIL - at times, it will be recorded but you'll see in the logs of something like AlfaOBD where it says "MIL not requested" where it saw a problem, but figured it was transient or didn't really have a solid answer as to code to set.

Otherwise, what's going to happen with a question like you posed, which is the same as "doctor, my arm hurts, what's wrong" - is people coming in and tossing mud at the wall to see what sticks.
Until you post all of the details, we'll be playing 20 questions.
Exactly under what circumstances do you get the misfire? Cold start? Hot/warm start?
Under load? Idling?
What are you using to determine cylinder 5 misfire? A cheap code reader?
A decent app or reader will give you more details - even suggesting whether it's ignition or fuel related.
Or, maybe you made a mistake somewhere in putting the "new motor" in - so start by triple-checking your own work.............
That's where I start if I do something major and run into a hitch - what changed? Oh, me - I worked on it. OK, I'll start there - maybe I missed something, didn't get a connection connected properly, etc.

Otherwise, we are all guessing - cylinder 5 misfire - could be fuel, could be ignition, could be something you did or didn't do, could be the PCM needs to learn - you didn't say at all how many miles you put on since the misfire!
Did it misfire right out of the gate?

I've changed plenty of 5.0s and 5.4s never messed with jeeps or 6 cylinders, as stated it was a last minute thing last night to attempt fire up so really am just looking for some ideas to throw at it when I get off work today. The misfire came right off start up, truck is still on stands but has slight rough idle with cylinder 5

 

[LouisvEarlleJT]

Did you check cylinder 5 for spark?

 

[whysoserious]

Hello,

Of course our 2020 gladiator ended up with the dreaded cylinder 3 misfire after 50k miles and of course warranty weaseled their way out of doing anything about it. We went out and bought a whole brand new long block heads and timing attached from the dealer and did the change ourselves, as we've changed plenty of motors in the passed. Upon first start of the new motor it now has a cylinder 5 misfire, we haven't looked into it to hard yet but being brand new factory plugs and the coil hadn't had a problem before what are yalls thoughts?

Swap the coil, then the plugs. See if the misfire moves.

 

[Minty JL]

Old school and noid light on the injector. Need to determine whether its a fuel or fire misfire.

Did the harness get depinned, nicked or stretched? More variables beyond the simple plugs, coils and injectors.

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