Odd misfire at idle on 5.3

[TexasLC]

My ‘21 5.3 has been absolutely trouble free for the last 31,000 miles.

However in the last couple of months I’ve witnessed this weird misfire/timing issue where the engine acts likes it’s out of balance and going to shut off.

It only does it at idle for maybe 1-2 actual seconds and then stops, never to be witnessed again for a couple of weeks. Also the tachometer needles does NOT move indicating a change in RPMs. This is baffling to me.

It’s probably happened a total of 4 times in the last 4 months.

Thoughts on what that could possibly be?

 

[Micahsd]

I’ve had that a few times too. It’s more than the usual shudder at idle and is an obvious misfire for a half a second or so. No lights illuminate or anything when it happens.

I’m not sure if it’s a fluke or the quality of the gas (I usually do put in 87 octane w/10% Ethanol that’s Top Tier rated) so I’m not sure what it could be either.

I have had the lifter issue occur at 9,100 miles although the dealer inky replaced once side so I’m waiting for the other side to go bad and currently at 15k miles.

 

[WalleyeMikeIII]

There is a TSB for engine shudder, caused by cam shaft actuator. Maybe this is your issue??

https://static.nhtsa.gov/odi/tsbs/2021/MC-10201315-9999.pdf

 

[TexasLC]

I’ve had that a few times too. It’s more than the usual shudder at idle and is an obvious misfire for a half a second or so. No lights illuminate or anything when it happens.

I’m not sure if it’s a fluke or the quality of the gas (I usually do put in 87 octane w/10% Ethanol that’s Top Tier rated) so I’m not sure what it could be either.

I have had the lifter issue occur at 9,100 miles although the dealer inky replaced once side so I’m waiting for the other side to go bad and currently at 15k miles.

Exactly right. No lights, no warnings, no rpm tach bouncing.

I thought about gas possibly too but it’s too infrequent I think. I run 87 also. And it never happens when the motor is moving through a rev range.

 

[TexasLC]

There is a TSB for engine shudder, caused by cam shaft actuator. Maybe this is your issue??

https://static.nhtsa.gov/odi/tsbs/2021/MC-10201315-9999.pdf

So this never is observed or felt while actually driving or when the motor is at any rpm above idle.

So while sitting at a light or in a parking spot or driveway is only when I’ve observed it.

Looking back it happened early on too but it was maybe once ever other month and just seemed like a fluke. But this past couple of months definitely has been more noticeable.

I’m stumped…

 

[Saltydog]

You know this happened to us about 4 months ago while at a stop light, no lights no messages and it has never come back. Now I have some idea of what it could be.

 

[TexasLC]

You know this happened to us about 4 months ago while at a stop light, no lights no messages and it has never come back. Now I have some idea of what it could be.

what idea could that be? : )

 

[Fless]

So this never is observed or felt while actually driving or when the motor is at any rpm above idle.

So while sitting at a light or in a parking spot or driveway is only when I’ve observed it.

Looking back it happened early on too but it was maybe once ever other month and just seemed like a fluke. But this past couple of months definitely has been more noticeable.

I’m stumped…

 

[TexasLC]

View attachment 386286

This never happens while driving and doesn't mimic anything to do with the transmission.

It only happens at idle.

 

[WalleyeMikeIII]

This never happens while driving and doesn't mimic anything to do with the transmission.

It only happens at idle.

I'd still recommend having the dealer look at it in light of that bulletin. It is possible that there is shudder you can't even feel that they see on the system when monitoring it...

Or, live w/ it till it gets worse.