HP Tuners for 3.6 models - Fixing what Jeep won’t

[bmpcamry09]

My brand new 2025 JL 3.6 has the now famous hesitation/stutter problem at low RPM that Stellantis refuses to push a PCM update out to address. With a background and deep “hobby” of tuning on the HP Tuners platform for people locally and on the web, I couldn’t help but believe this issue is a tuning issue. Several master techs who have looked into the issue believe it is a tuning problem.

I’m working on developing a solution via HP Tuners. Most of my tuning experience is on Ford Ecoboost and Gen 3/4/5 GM stuff, so this will be a little bit of a learning curve, but I think we will be able to fix this surge issue before Stellantis does.

Just sent off my PCM today for unlocking. More to come once I have time to datalog and do some initial testing! Here is my first YT video explaining PCM removal.

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[Rickythetruk]

That's awesome man, the low RPM hesitation on these 3.6s is driving everyone nuts and you're probably right that it's just a fueling or timing table issue that could be fixed pretty easily if Stellantis actually cared.

 

[RubyRuin]

Definitely keeping an eye on this thread, I'm surprised no one's picked up on tuning these GPEC5 PCMs since they're unlocked for over a year now. I had a 2024 JLR 6 speed (And now with a 2026 JLR 6 speed on order) that would have been perfectly fine if the low RPM hesitation issues are fixed.

 

[bmpcamry09]

I’m about 90 percent positive after looking at both GPEC2 and GPEC5 files that this hesitation is due to the way the intake variable cam timing tables are set up, paired with the EGR system and the accompanying spark timing tables that are EGR modifiers. I think the EGR effect paired with wack timing tables are causing a false knock detonation event that is making the engine suddenly pull timing. But I’ll know for sure here in about a week when my PCM is back and I can build a good datalog channel and do some driving.

 

[Fatfreewilly]

Subscribed! Hoping we finally see what the dumb issue is.

2024 6 speed here.

 

[bmpcamry09]

Subscribed! Hoping we finally see what the dumb issue is.

2024 6 speed here.

Appreciate it. Once I figure out the issue, and I can catch it on a datalog, I plan on making a video explaining the issue in detail.

 

[cheapjeepJL]

my hero.

 

[AmericanPatriot100]

2025 6spd here. Subbed.

 

[GabeBoyTheGreat]

If you start a crowdfunding campaign like you mentioned in the other thread, I will contribute. I know you are investing a lot.

 

[cheapjeepJL]

If you start a crowdfunding campaign like you mentioned in the other thread, I will contribute. I know you are investing a lot.

X2

 

[bmpcamry09]

If you start a crowdfunding campaign like you mentioned in the other thread, I will contribute. I know you are investing a lot.

I wouldn’t even know where to begin with that, but I’ll do some digging. I’m a little green with the whole YouTube thing, but I’d love to share my passion and knowledge on tuning stuff and I think these have some potential. Already forked over the money but if this goes as planned, I’d like to be the go to guy for forum people who want to tune their JL to stay factory reliable but make it that much better to drive. Will upload another video soon discussing the issue and my game plan.

 

[GabeBoyTheGreat]

I wouldn’t even know where to begin with that, but I’ll do some digging. I’m a little green with the whole YouTube thing, but I’d love to share my passion and knowledge on tuning stuff and o think these have some potential. Already forked over the money but if this goes as planned, I’d like to be the go to guy for forum people who want to tune their JL to stay factory reliable but make it that much better to drive. Will upload another video soon discussing the issue and my game plan.

Understood. I don't really know much about setting one up. However, if you have PayPal, you can PM me, and I will send a little (keyword on "little") something your way.

 

[bmpcamry09]

I've got Paypal and Venmo, and if anyone is interested in contributing to the project, shoot me a DM on here.

 

[bmpcamry09]

If anyone can chime in, I am looking for a summary of other tune related things you would like to see improved on your JL. Here is what I plan on working on:

-Creating a more linear throttle response, not so spongy
-Changing when and where the torque converter locks up, i think lockup in 2nd gear is a bit extreme.
-Disabling auto start stop so button no longer needs to be pressed every start up.
-Allowing the trans to ride in 4th and 5th gear more in town not being so eager to get into high gear to help with engine bogging down.
-Changing cooling fan activation points, because coolant temps get high in summer.
-Changing VVT and cam timing to help with low end grunt around town.
-Taking some of the slop out of normal in town shifting, shifting seems a little too sluggish at part throttle, seems okay at wide open throttle might tweak WOT just a little bit though.
-Truely optimizing spark timing for those who only run 87 fuel, sure Jeep says it's "safe" and sure it is by the book, but trust me, I've tuned enough modern vehicles to know that your enigne is borderline detonating on 87 fuel no matter what your manufacturer says, and I'd rather not have the engine ping and bouncing off the knock sensors.
-Maybe add about 20-30 HP with some extra timing for those willing to run premium fuel.

 

[GabeBoyTheGreat]

If anyone can chime in, I am looking for a summary of other tune related things you would like to see improved on your JL. Here is what I plan on working on:

-Creating a more linear throttle response, not so spongy
-Changing when and where the torque converter locks up, i think lockup in 2nd gear is a bit extreme.
-Disabling auto start stop so button no longer needs to be pressed every start up.
-Allowing the trans to ride in 4th and 5th gear more in town not being so eager to get into high gear to help with engine bogging down.
-Changing cooling fan activation points, because coolant temps get high in summer.
-Changing VVT and cam timing to help with low end grunt around town.
-Taking some of the slop out of normal in town shifting, shifting seems a little too sluggish at part throttle, seems okay at wide open throttle might tweak WOT just a little bit though.
-Truely optimizing spark timing for those who only run 87 fuel, sure Jeep says it's "safe" and sure it is by the book, but trust me, I've tuned enough modern vehicles to know that your enigne is borderline detonating on 87 fuel no matter what your manufacturer says, and I'd rather not have the engine ping and bouncing off the knock sensors.
-Maybe add about 20-30 HP with some extra timing for those willing to run premium fuel.

All of this sounds good to me. I found this thread about the RPM Extreme Fan controller. In the OP, there is an image that shows the fan settings based on temperature. That would probablybe a good baseline: https://www.jlwranglerforums.com/forum/threads/rpm-fan-controller-results-on-off-road.128374/

Looks like the fan kicks to 100% at 218+ which seems reasonable to me. I would like to keep my temps below 220 if possible. I think the stock setting is like 232 for 100% fan.

I would also recommend watching this video from Livernois showcasing their dyno results from their GPEC-2 tune:

It would be nice if you could get rid of that torque dip between 4k and 5k RPMs like Livernois did.

Any torque improvements for RPMs < 2k would also be welcomed.

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