2021 JLU 2.0 Turbo - Rough Idle

[IronRiverJLU]

Hi Guys - I know there have been discussions on this in the past, but I’m curious if there’s any new info about it… My JLU had 24k miles on it when purchase last summer (2023). It idled so quietly, you couldn’t even tell it was on… However, as time has gone on, it started idling rough. Not all of the time… but it has gotten progressively worse. I’m now right at 40k miles and it idles rough pretty much 100% of the time. The whole Jeep vibrates. If I set a water bottle on the dash, the water bounces like crazy.

I’ve been meticulous with maintenance. Always run premium gas and regular oil changes. I DID take it to the dealership and they said they “couldn’t duplicate the issue”. ? No check engine light. The oil pressure appears to be fine and it’s not running hot. I have done two fuel treatments but those haven’t helped at all.

Anyone have experience with this that has gotten to the bottom of the issue?

Any help is appreciated. Thanks!

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[Jeep Wick]

Hi Guys - I know there have been discussions on this in the past, but I’m curious if there’s any new info about it… My JLU had 24k miles on it when purchase last summer (2023). It idled so quietly, you couldn’t even tell it was on… However, as time has gone on, it started idling rough. Not all of the time… but it has gotten progressively worse. I’m now right at 40k miles and it idles rough pretty much 100% of the time. The whole Jeep vibrates. If I set a water bottle on the dash, the water bounces like crazy.

I’ve been meticulous with maintenance. Always run premium gas and regular oil changes. I DID take it to the dealership and they said they “couldn’t duplicate the issue”. ? No check engine light. The oil pressure appears to be fine and it’s not running hot. I have done two fuel treatments but those haven’t helped at all.

Anyone have experience with this that has gotten to the bottom of the issue?

Any help is appreciated. Thanks!

Maybe carbon buildup? You'll need someone to put a borescope in the intake to look. Walnut blasting is the fix.

 

[IronRiverJLU]

Thank you for the reply! So, carbon buildup would make it idle rough like that?

 

[jellis4148]

Did you run Top Tier Fuel or just any premium gas?

 

[IronRiverJLU]

Did you run Top Tier Fuel or just any premium gas?

Great question. I typically just use whatever the highest grade gas is at whichever gas station I go to. Typically at Shell or Wawa (that’s what’s closest to my house.) What would you consider Top Tier? Will it make that much of a difference?

 

[wcjeep]

Thank you for the reply! So, carbon buildup would make it idle rough like that?

Check YouTube for carbon buildup on valves. On other vehicles some people add Oil Catch Cans to reduce the intake carbon buildup.

 

[Heimkehr]

My JLU had 24k miles on it when purchased last summer (2023).

...as time has gone on, it started idling rough. Not all of the time… but it has gotten progressively worse. I’m now right at 40k miles and it idles rough pretty much 100% of the time.

Any help is appreciated. Thanks!

In no particular order:

Air filters are due every 30K miles, and 40K isn't too early to install new spark plugs as a prophylactic measure, or as a potential fix here (doubly so if you don't know the vehicle's precise maintenance history prior to your purchase.)

Have a look also at the serpentine belt and all of the pulleys, with the engine running, to ensure smooth functioning. Examine every under-hood harness connector to ensure that they're properly seated and secured. Press down on every fuse and relay in the fuse box (aka PDC) to ensure that they're also properly snug.

Yes, it is possible that carbon buildup may have accumulated to the point that walnut blasting, for example, might be indicated.

-------------------

Some years ago, I had terrible vibration on a still-new VW Golf that I had just purchased. The symptoms appeared suddenly, but otherwise matched the description of the current condition of your engine. In my case, a faulty spark plug coil was the culprit. It was replaced under warranty and the engine was instantly restored to smooth running.

 

[IronRiverJLU]

In no particular order:

Air filters are due every 30K miles, and 40K isn't too early to install new spark plugs as a prophylactic measure, or as a potential fix here (doubly so if you don't know the vehicle's precise maintenance history prior to your purchase.)

Have a look also at the serpentine belt and all of the pulleys, with the engine running, to ensure smooth functioning. Examine every under-hood harness connector to ensure that they're properly seated and secured. Press down on every fuse and relay in the fuse box (aka PDC) to ensure that they're also properly snug.

Yes, it is possible that carbon buildup may have accumulated to the point that walnut blasting, for example, might be indicated.

-------------------

Some years ago, I had terrible vibration on a still-new VW Golf that I had just purchased. The symptoms appeared suddenly, but otherwise matched the description of the current condition of your engine. In my case, a faulty spark plug coil was the culprit. It was replaced under warranty and the engine was instantly restored to smooth running.

All fantastic info. We’ll give that stuff a try… Thank you!!

 

[jellis4148]

Great question. I typically just use whatever the highest grade gas is at whichever gas station I go to. Typically at Shell or Wawa (that’s what’s closest to my house.) What would you consider Top Tier? Will it make that much of a difference?

Yes, it makes a huge difference. I've seen so many DI engines come in that need a top engine clean, and they used regular gas instead of top tier. It doesn't cost anymore to purchase Top Tier fuel. Shell is Top Tier, but it doesn't look like WAWA is. Here is a link to the website. Top Tier fuel will help prevent the carbon build up, and you don't need a catch can.




https://www.toptiergas.com/gasoline-brands/

 

[IronRiverJLU]

Yes, it makes a huge difference. I've seen so many DI engines come in that need a top engine clean, and they used regular gas instead of top tier. It doesn't cost anymore to purchase Top Tier fuel. Shell is Top Tier, but it doesn't look like WAWA is. Here is a link to the website. Top Tier fuel will help prevent the carbon build up, and you don't need a catch can.




https://www.toptiergas.com/gasoline-brands/

The more you know…. lol Thank you!!

 

[Kahuna]

I had my 2020 2T serviced at just under 60K and needed the paperwork filled out by dealer for extended warranty. They were being so helpful and quick with turnaround to get me in under mileage that I decided to let them do the classic "Throttle Body" clean. Shockingly I actually noticed a difference in idle right away. Now mine was not having the rough idle yours was but maybe it is something to look into.

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