2021 Rubicon (3.6L) - Rough idle, loss of power, misfiring. Dealer can't replicate. Now what?

[ace3]

Bought a 2021 Rubicon Unlimited two weeks ago. After taking delivery, I noticed the idle was a little rough. I chalked that up to it being brand new and didn’t think anything of it. At least a couple times a day since then, there will be some hesitation or jerking/misfiring while the engine is under power.

Earlier this week I stopped at a stop light. When I drove off, engine power dropped considerably and the check engine light started blinking. I was right across the street from a Jeep dealership, so I dropped it off at their service department.

I picked it up yesterday when they said it was ready. Their service report states that there was a misfire code (P0301) stored in the computer, but the tech couldn’t duplicate the problem. They pulled a fuel sample and everything checked out there.

After picking up the Jeep, the issues are absolutely still present. Idle is rough, and when giving the engine even moderate power, you can absolutely tell that it’s misfiring. With only having ~850 miles on the Jeep, this is definitely a concern. According to the service invoice, they put 5 miles on the Jeep. In my opinion, there's no way on earth they wouldn't have noticed the misfire in 5 miles of driving.

Any recommendations? Take it back to the same dealer? Different dealer? Reach out to Jeep?

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[FormerF150Owner]

Bought a 2021 Rubicon Unlimited two weeks ago. After taking delivery, I noticed the idle was a little rough. I chalked that up to it being brand new and didn’t think anything of it. At least a couple times a day since then, there will be some hesitation or jerking/misfiring while the engine is under power.

Earlier this week I stopped at a stop light. When I drove off, engine power dropped considerably and the check engine light started blinking. I was right across the street from a Jeep dealership, so I dropped it off at their service department.

I picked it up yesterday when they said it was ready. Their service report states that there was a misfire code (P0301) stored in the computer, but the tech couldn’t duplicate the problem. They pulled a fuel sample and everything checked out there.

After picking up the Jeep, the issues are absolutely still present. Idle is rough, and when giving the engine even moderate power, you can absolutely tell that it’s misfiring. With only having ~850 miles on the Jeep, this is definitely a concern. According to the service invoice, they put 5 miles on the Jeep. In my opinion, there's no way on earth they wouldn't have noticed the misfire in 5 miles of driving.

Any recommendations? Take it back to the same dealer? Different dealer? Reach out to Jeep?

Your problem sounds like the same exact issue I have had. My wife has a 2016 JK with a 3.6 and I thought from day one my engine had a slight misfire but hers runs like a smooth running sewing machine. At 437 miles the CEL started flashing. It's been in the shop since 10/15 but I took it to another shop yesterday. I hope you get your issue resolved. I haven't had any resolve yet.

 

[JeepCares]

Bought a 2021 Rubicon Unlimited two weeks ago. After taking delivery, I noticed the idle was a little rough. I chalked that up to it being brand new and didn’t think anything of it. At least a couple times a day since then, there will be some hesitation or jerking/misfiring while the engine is under power.

Earlier this week I stopped at a stop light. When I drove off, engine power dropped considerably and the check engine light started blinking. I was right across the street from a Jeep dealership, so I dropped it off at their service department.

I picked it up yesterday when they said it was ready. Their service report states that there was a misfire code (P0301) stored in the computer, but the tech couldn’t duplicate the problem. They pulled a fuel sample and everything checked out there.

After picking up the Jeep, the issues are absolutely still present. Idle is rough, and when giving the engine even moderate power, you can absolutely tell that it’s misfiring. With only having ~850 miles on the Jeep, this is definitely a concern. According to the service invoice, they put 5 miles on the Jeep. In my opinion, there's no way on earth they wouldn't have noticed the misfire in 5 miles of driving.

Any recommendations? Take it back to the same dealer? Different dealer? Reach out to Jeep?

Hello @ace3
We sincerely regret to hear that you are facing this concern with your new Jeep. Please send our team a private message with your VIN and mileage. We will gladly offer our the additional support of a specialist during your next dealer visit.

Kathryn
JeepCares

Your problem sounds like the same exact issue I have had. My wife has a 2016 JK with a 3.6 and I thought from day one my engine had a slight misfire but hers runs like a smooth running sewing machine. At 437 miles the CEL started flashing. It's been in the shop since 10/15 but I took it to another shop yesterday. I hope you get your issue resolved. I haven't had any resolve yet.

@FormerF150Owner
Hi there, we are sorry to hear that this concern has yet to be resolved for you! Please know that our team is available via private message to assist during any dealer service. Please do not hesitate to reach out for further support alongside your dealer!

Kathryn
JeepCares

 

[ace3]

Update ... Took it to another dealer on Friday. Should have taken it there in the first place - their customer service was light years better than the first one.

They just called and said it was a faulty Variable Valve Timing Solenoid. Will pick it up later today - hopefully everything is taken care of!

 

[gofastguy]

Update ... Took it to another dealer on Friday. Should have taken it there in the first place - their customer service was light years better than the first one.

They just called and said it was a faulty Variable Valve Timing Solenoid. Will pick it up later today - hopefully everything is taken care of!

Glad to hear they found this for you. My 2018 3.6 had the exact same symptoms when new and this was the fix. I'm not sure if this is connected, but mine has always idled rougher than others but of course the service people cannot notice this, and there have been 3 instances of unexplainable completely dead engine over the years which have resolved themselves after 15-20 minutes, which also seems impossible to diagnose. The good news is the dead engine thing hasn't happened in a little over a year.

 

[ace3]

Glad to hear they found this for you. My 2018 3.6 had the exact same symptoms when new and this was the fix. I'm not sure if this is connected, but mine has always idled rougher than others but of course the service people cannot notice this, and there have been 3 instances of unexplainable completely dead engine over the years which have resolved themselves after 15-20 minutes, which also seems impossible to diagnose. The good news is the dead engine thing hasn't happened in a little over a year.

Wow - no kidding. Sorry to hear of your issues the last few years!
I'll be keeping a close eye on it. This is my 7th Jeep (6th one purchased new) and this is the first one to have any sort of issues. Hope this solves it for good!

 

[FormerF150Owner]

Update ... Took it to another dealer on Friday. Should have taken it there in the first place - their customer service was light years better than the first one.

They just called and said it was a faulty Variable Valve Timing Solenoid. Will pick it up later today - hopefully everything is taken care of!

Got mine back today from the 2nd dealer and it's running great thus far. They said it was due to a faulty spark plug. It's been in the shop since 10/15 - just glad to have it back!

 

[neil]

Got mine back today from the 2nd dealer and it's running great thus far. They said it was due to a faulty spark plug. It's been in the shop since 10/15 - just glad to have it back!

2 weeks for a spark plug. Sorry. You should publicly share this shop so locals can avoid.

 

[FormerF150Owner]

2 weeks for a spark plug. Sorry. You should publicly share this shop so locals can avoid.

The 2nd shop went back to the first shop as they are a sister dealership and kinda got in their hair. They asked the 1st shop "what were you doing to this guy"? I'm just blessed this wasn't my daily driver. The 2nd shop took it in last Thursday and let me know they couldn't get to it until today. The fixed the issue the same day the looked at it.

 

[SpeedyJEP]

Same problem here on a 3.6 2021 JLUR with < 1000 miles, minus the computer code. Constant misfire that causes the vehicle to stutter and buck, particularly between 2k and 3k RPMs. No trouble code; so far the dealer has replaced an O2 sensor and a coil pack over the past week to no avail. They asked me to drive it until it throws a code, but the misfire is pervasive and I don't want to cook the cat with all that unburned fuel.

They're trying new plugs today, will update with results.

 

[ace3]

Same problem here on a 3.6 2021 JLUR with < 1000 miles, minus the computer code. Constant misfire that causes the vehicle to stutter and buck, particularly between 2k and 3k RPMs. No trouble code; so far the dealer has replaced an O2 sensor and a coil pack over the past week to no avail. They asked me to drive it until it throws a code, but the misfire is pervasive and I don't want to cook the cat with all that unburned fuel.

They're trying new plugs today, will update with results.

Ask them to test the variable valve timing solenoid. My dealer said it was the 5th one they had replaced on '21 wranglers.

 

[SpeedyJEP]

Problem apparently resolved by the dealer after I asked them to keep looking. The work order indicates they replaced all six spark plugs per TSB 09-013-20 issued just a few days ago on 12/5/2020. Night and day difference on the drive home - no misfire/stutter/bucking, and the idle is smooth without the regular dropout previously experienced.

 

[AU_JLU]

T

Problem apparently resolved by the dealer after I asked them to keep looking. The work order indicates they replaced all six spark plugs per TSB 09-013-20 issued just a few days ago on 12/5/2020. Night and day difference on the drive home - no misfire/stutter/bucking, and the idle is smooth without the regular dropout previously experienced.

thanks for this information. I tried to search this TSB so I could take it to my dealer. I couldn’t find anything online. Any chance you have a link with more detail?

 

[SpeedyJEP]

T
thanks for this information. I tried to search this TSB so I could take it to my dealer. I couldn’t find anything online. Any chance you have a link with more detail?

I've unfortunately been unable to find any further info beyond the TSB number and release date mentioned on the work order. For what it's worth, I've put a few hundred miles on the vehicle since and the problem does appear resolved due to the new spark plugs.

 

[Rubicon1951]

Bought a 2021 Rubicon Unlimited two weeks ago. After taking delivery, I noticed the idle was a little rough. I chalked that up to it being brand new and didn’t think anything of it. At least a couple times a day since then, there will be some hesitation or jerking/misfiring while the engine is under power.

Earlier this week I stopped at a stop light. When I drove off, engine power dropped considerably and the check engine light started blinking. I was right across the street from a Jeep dealership, so I dropped it off at their service department.

I picked it up yesterday when they said it was ready. Their service report states that there was a misfire code (P0301) stored in the computer, but the tech couldn’t duplicate the problem. They pulled a fuel sample and everything checked out there.

After picking up the Jeep, the issues are absolutely still present. Idle is rough, and when giving the engine even moderate power, you can absolutely tell that it’s misfiring. With only having ~850 miles on the Jeep, this is definitely a concern. According to the service invoice, they put 5 miles on the Jeep. In my opinion, there's no way on earth they wouldn't have noticed the misfire in 5 miles of driving.

Any recommendations? Take it back to the same dealer? Different dealer? Reach out to Jeep?

My 2021 3.6L Rubicon started having cold start (only) idle issues at 300 miles. The engine had a lumpy or galloping idle. After three mornings of doing this, on the fourth day the engine stalled and the check engine light came on. Dealer had vehicle for 8 days. Dealer followed the FCA "flow chart" to correct the problem. Even called Jeep in Auburn Hills, MI. Still no fix. Finally the mechanic checked the fuel pressure at the fuel rail and had 20 psi where the spec is 58 psi. This pressure check was NOT in the FCA flow chart to diagnose the problem. Replaced the in-tank full pump and fuel PCM. NO issue since "corrected" but keeping my fingers crossed. It's only been a 100 miles or so since the fix.

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