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

[bmpcamry09]

Rev hang is a big problem on the automatics, too. That is the #2 issue I'm hoping will be solved. Hesitation is #1.

Can you describe the rev hang issue on the automatic? I haven't experienced it on mine. Is this something that happens in drive? Or are you talking about how the engine goes back to idle after reving?

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[Badunit]

Sure. I'd have to go out and time stuff to give you an accurate reproducible way to make it happen but the gist of it is:

1. Moving along normally
2. Floor it for a second
3. It downshifts a few gears and the revs go way up (as expected) and you start accelerating
4. Take foot off throttle quickly and completely
5. It remains downshifted, it keeps fueling (might even still be accelerating at first), then it slowly backs down over a few seconds and eventually upshifts. What it should do is chop the throttle and there should be immediate engine braking but that's not what it does.

Similar thing if you want to jam the throttle to get the rear to break free in the snow to slide around a little. It doesn't quit immediately when you let off the gas.

 

[bmpcamry09]

Sure. I'd have to go out and time stuff to give you an accurate reproducible way to make it happen but the gist of it is:

1. Moving along normally
2. Floor it for a second
3. It downshifts a few gears and the revs go way up (as expected) and you start accelerating
4. Take foot off throttle quickly and completely
5. It remains downshifted, it keeps fueling (might even still be accelerating at first), then it slowly backs down over a few seconds and eventually upshifts. What it should do is chop the throttle and there should be immediate engine braking but that's not what it does.

Similar thing if you want to jam the throttle to get the rear to break free in the snow to slide around a little. It doesn't quit immediately when you let off the gas.

Got it, I'll be sure to try to replicate that and catch it on a datalog. Could be a few things. First thing that comes to mind is how the friction torque is modeled. I've had success on other makes/models of changing these tables to get the engine to fall back to idle faster. Could be an airflow model issue. I imagine it could have something Stellantis is doing on purpose for emissions/catalytic converter reasons.

On the automatic models, there is an "aggression model" that kicks in and completely changes shift scheduling based on driver aggression. Think of it like a police pursuit mode that Ford uses. It could be responsible for excess hang/rev on automatic models.

 

[PotterJLUR]

It would be really hard for me to want to void my full powertrain warranty for this issue, vs. waiting on a eventual OEM pcm update. Mopar makes dealer techs send in "vehicle scan reports" that show configuration, software level, ect. on powertrain warranty claims.

 

[bmpcamry09]

It would be really hard for me to want to void my full powertrain warranty for this issue, vs. waiting on a eventual OEM pcm update.

I'm making these safe enough you won't have any tune related failures, I'm putting it on my wifes daily driver that she hauls my children in.

It would be difficult for a dealer to prove anything happened because of a tune. Plus this platform doesn't flag the PCM as not being factory calibration like the Scat Packs and Hellcats do. Even if it did, I have a way around that.

The OS ID, PCM part number, and everything else remains the same. A dealer scan tool can't see that anything has been changed. They can see a "flash count" but that would be it. The only thing I could see getting voided is if an issue is related to a PCM failure, they won't warranty it since it's been opened and unlocked.

Also, if you buy your own MPVI device, you'll be able to flash right back to stock any time you want.

 

[alphawolff]

Not really wanting to send my original pcm out. Could I purchase a new blank from Jeep send that to them along with my vin#. Or would I need to bring it to a dealer have them program it for my vin# then send it out?
68568654AB is what I show for the part# and it is pretty cheap at only $130.

For that small added cost I would much rather keep my original stock and use the backup to play with.

I actually did this with my 392 as I didn't know if it would throw the aftermarket calibration DTC. Ended up being totally unnecessary, but yeah, buy a second PCM and have the dealership program it. Ship the original out and keep the second one as the OEM backup

It would be really hard for me to want to void my full powertrain warranty for this issue, vs. waiting on a eventual OEM pcm update. Mopar makes dealer techs send in "vehicle scan reports" that show configuration, software level, ect. on powertrain warranty claims.

I've gone over my 392 (and supercharged 16 JK when I had it) and never found any indication whatsoever for custom tuning. The config and software revisions are identical. I suspect mopar, other than the hellcat custom calibration DTC flags, simply doesn't account for people getting custom tunes. Most of our vehicles arent enthusiast vehicles, and not many people bother tuning NA vehicles at all compared to something like Subaru where every kid around throws a tune on it.

I'm making these safe enough you won't have any tune related failures, I'm putting it on my wifes daily driver that she hauls my children in.

It would be difficult for a dealer to prove anything happened because of a tune. Plus this platform doesn't flag the PCM as not being factory calibration like the Scat Packs and Hellcats do. Even if it did, I have a way around that.

The OS ID, PCM part number, and everything else remains the same. A dealer scan tool can't see that anything has been changed. They can see a "flash count" but that would be it. The only thing I could see getting voided is if an issue is related to a PCM failure, they won't warranty it since it's been opened and unlocked.

Also, if you buy your own MPVI device, you'll be able to flash right back to stock any time you want.

Not that this is at all relevant here, but the PCM calibration DTC that gets thrown is actually thrown by the BCM, not the PCM. And once it's thrown it's permanent, you cannot clear it. On my 392 I even bought a second BCM anticipating this but ended up wasting the money as it never threw. Disabling the DTC in the PCM doesn't accomplish anything, as the PCM doesn't throw it. I suspect on certain performance vehicles (hellcats, mainly) have this additional BCM logic to check for it.

 

[Jerkwater]

It would be difficult for a dealer to prove anything happened because of a tune. Plus this platform doesn't flag the PCM as not being factory calibration like the Scat Packs and Hellcats do. Even if it did, I have a way around that.

The OS ID, PCM part number, and everything else remains the same. A dealer scan tool can't see that anything has been changed. They can see a "flash count" but that would be it. The only thing I could see getting voided is if an issue is related to a PCM failure, they won't warranty it since it's been opened and unlocked.

Just jumping in the thread here to ask about this.

Are the 2025s really like this? I used HP Tuners to change some settings in an unlocked (and flashed with my stock program) ebay PCM in my 2018 JLU, which has a 3.6. Ever since, there has been a code (but no CEL) about aftermarket calibration detected. Its not stored in the PCM, because it is still there even if I put my stock PCM back in.

I think I read that the code is stored in the BCM. I actually have a second BCM programmed for my JLU as a spare,. I haven't tried putting it in with the stock PCM to see if the code would go away.

 

[bmpcamry09]

Just jumping in the thread here to ask about this.

Are the 2025s really like this? I used HP Tuners to change some settings in an unlocked (and flashed with my stock program) ebay PCM in my 2018 JLU, which has a 3.6. Ever since, there has been a code (but no CEL) about aftermarket calibration detected. Its not stored in the PCM, because it is still there even if I put my stock PCM back in.

I think I read that the code is stored in the BCM. I actually have a second BCM programmed for my JLU as a spare,. I haven't tried putting it in with the stock PCM to see if the code would go away.

In my 2025 under the DTCs tab in VCM Editor, P1400 is already disabled. I’m not sure if the BCM throws a separate one. I haven’t seen it.

On the 2023 Scat Pack with the GPEC2A like your 2018, I did in fact have to go in and disable that code as it did throw it. After disabling it, never saw it again.

 

[Jerkwater]

In my 2025 under the DTCs tab in VCM Editor, P1400 is already disabled. I’m not sure if the BCM throws a separate one. I haven’t seen it.

On the 2023 Scat Pack with the GPEC2A like your 2018, I did in fact have to go in and disable that code as it did throw it. After disabling it, never saw it again.

Interesting. I didn't know you could disable DTCs - thanks!

 

[bmpcamry09]

Interesting. I didn't know you could disable DTCs - thanks!

If you don’t have parameter access to DTC codes, you’ll have to take the emissions training course online on HPT website and get the advanced parameters. It’s been years since I had to do that but I believe it’s still that way.

 

[Badunit]

I don't care if they know. I just want it to run correctly. I don't need any additional power. I don't need torque management turned down (if it is saving the engine or other components). I just want it to run right.

 

[bmpcamry09]

It’s coming!

I tracked down a Grand Cherokee file. Same engine. Same trans. Dramatic differences in cam and spark timing set up. My last GC I owned was silky smooth with same engine. So I’m going to do some playing around with settings from that as well.

 

[wanted]

Looking at my particular file, it appears all parameters for E85 are already repopulated, there is a toggle switch and it doesn’t appear much more would need to change. Obviously I would want to verify through Datalogging, but at least on my 2025 calibration, flex fuel enabling appears to be just a toggle switch and little else since all the “Alcohol” or E85 related tables are populated with what appears to be good data.

E85 is great in DI and forced induction stuff. I’ve done a lot of E85 tuning with Ford 3.5 Ecoboost stuff. On those a lot of it is dependent on the in tank fuel pump and injectors being able to flow the extra fuel required. I imagine this JL wouldn’t need any fuel upgrades since it’s only PI and no turbo, but I would have to test and see. im not sure I’ll personally get into E85 testing as our local E85 usually tests out at E70, and this is just a side thing for me.

Wait....if I'm reading this correctly does this imply that our jeeps can measure alcohol content and don't need an additional flex fuel sensor wired in, or am I grossly misreading your reply?

 

[bmpcamry09]

Wait....if I'm reading this correctly does this imply that our jeeps can measure alcohol content and don't need an additional flex fuel sensor wired in, or am I grossly misreading your reply?

I really dont know, sorry, I just can see that flex fuel OS capability is already enabled on my 2025, dont know if it has an alcohol sensor or if it just picks up on the swing in fuel trims and assumes alcohol content.

Here are a few screenshots to show you what I was talking about. Flex fuel is a click option and its already populated in the OS, and all alcohol related compensations in the tables are already generated throughout the file

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[bmpcamry09]

UPDATE - Some of you wont like it..........

First, I want to preface this by saying I am still early on in testing. I have had OUTSTANDING results with down low torque improvements, throttle response, top end power, transmission shifting, and all the other little tidbits that can be improved on with quality tuning. I know I'll be able to deliver on that.....I pride myself on integrity and being forthcoming, and I'll always be that way.

HOWEVER,

This low RPM/low throttle stutter/hesitation/timing retard/VVT/unknown issue is kicking my ass. Hard.

This HURTS me to say, but I think I was wrong when I said I thought I had already fixed the stutter. I think my changes only masked the issue. I'll explain my changes thus far and what I think was masking the stutter below.......It appears I had only found ways to mask it. Reviewing datalogs, I can still see a visible drop in spark advance around 1500-2000 RPMs and feel a torque surge.

I'm getting frustrated, but not giving up. I am optimistic that once I have all the GPEC5 datalog PIDS at my disposal that I will uncover something new. I am at revision number 30 right now........Yes.....30.........Each one of those revisions has included a datalog session using the most basic PIDS I have access to at the moment. I have probably 24 hours of computer work and driving dedicated into this already, and I'm driving my wife nuts.

THINGS THAT I TRIED THAT MADE ZERO DIFFERENCE:

-Completely disabled VVT all together.
-Lock out intake cam at resting/idle/full retard position at affected RPM area.
-Completely disable knock sensors.
-Leave knock sensors on but reduce sensitivity.
-Copy timing and cam tables from earlier models of both Wrangler and G.C with
same engines.
-Use changes that the Pacifca 3.6 PUG engine has.
-Pull 10 degrees of timing from all spark tables
-Disable oil control valve cleaning cycle.

THINGS I TRIED THAT ACTUALLY MADE A DIFFERENCE, BUT WERE PROBABLY JUST MASKING

-Manually adding in intake cam advance up to 30 degrees in low RPM places - THIS MADE THE MOST DRAMATIC DIFFERENCE, BUT THE DATA STILL SHOWS A SHARP DROP IN SPARK TIMING. The data doesn't lie, this isn't a true "fix". That said, this change feels like it added 20-30 foot pounds of torque to everything below 3000 RPM.
-Not allowing torque converter to lock until 4th gear, - THIS ALSO MADE A DIFFERENCE, HOWEVER, I THINK THE SLIPPAGE OF THE TCC WAS JUST TAKING SHOCK AWAY, THIS WONT HELP YOU 6 SPEED GUYS. Plus, I observed higher trans fluid temps slipping the TCC until 4th, along with less than desirable shift feel.

I just wanted to make this post because I don't want to give people false hope. I'd rather disclose the progress than hide something, especially if you plan on paying me for a tune. Especially for you manual transmission guys, a great PCM calibration is going to be dependent on getting rid of this stutter and not just masking it.

Bear with me as I work through this, no matter what, I will be releasing tunes for this platform that will be backed with Dyno pulls and hard numbers. I am in touch with a local dyno already, and I will be video recording the whole dyno experience hopefully.

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