Steeper descents dangerous behavior

[jeeeep]

But this can happen in any gear, HI or LO range. As I recall ABS is turned off when you enter LO range, but it happens just the same. My regular dealer is not good, and my Jeep is my regular driver. They're pretty clueless, and I'm not leaving it with them.
Other than this, and a couple of annoyances I've corrected using the Tazer device, this is the best Jeep I've ever owned. And I've had quite a few, having 4-wheeled all my life.
(Don't know why I'm shown as a "new member", been on here since 2020)

it only works in 4LO, and it uses ABS to facilitate in the auto-braking

If it's too steep it doesn't work worth a crap, I've run into this on occasion

New member because you only have 15 posts, it based on your post activity, not length of time

 

[XT Carol]

it only works in 4LO, and it uses ABS to facilitate in the auto-braking

If it's too steep it doesn't work worth a crap, I've run into this on occasion

New member because you only have 15 posts, it based on your post activity, not length of time

Oh, understand about not enough posts.
I use and like Hill Descent mode and have used it on some pretty steep descents. But, I can see that on loose/slippery surfaces, no it couldn't do so much there.
But the issue we've been discussing happens even in 2WD regular driving. Really irritating, hard on brakes too. I've decided it's somehow temperature related, like if there's not enough air movement past some(?) sensor, it's worse.

 

[jeeeep]

Oh, understand about not enough posts.
I use and like Hill Descent mode and have used it on some pretty steep descents. But, I can see that on loose/slippery surfaces, no it couldn't do so much there.
But the issue we've been discussing happens even in 2WD regular driving. Really irritating, hard on brakes too. I've decided it's somehow temperature related, like if there's not enough air movement past some(?) sensor, it's worse.

are you saying when driving in 2wd on a flat road, hill descent turns on? if so, you need to have the dealer look into that.
HD should not work in 2WD, only 4LO - from the owner's manual

Hill Descent Control (HDC) — If Equipped
HDC is intended for low speed off road driving while in
4WD Low Range. HDC maintains vehicle speed while
descending hills during various driving situations. HDC
controls vehicle speed by actively controlling the brakes.
HDC has three states:
1. Off (feature is not enabled and will not activate).
2. Enabled (feature is enabled and ready but activation
conditions are not met, or driver is actively overriding
with brake or throttle application).
3. Active (feature is enabled and actively controlling vehicle
speed).

HDC will be deactivated but remain available if any of the
following conditions occur:
• Driver overrides HDC set speed with throttle or brake
application.
• Vehicle speed exceeds 20 mph (32 km/h) but remains
below 40 mph (64 km/h).
• Vehicle is on a downhill grade of insufficient magnitude,
is on level ground or is on an uphill grade.
• Vehicle is shifted to park.

Disabling HDC
HDC will be deactivated and disabled if any of the
following conditions occur:
• The driver pushes the HDC switch.
• The driveline is shifted out of 4WD Low Range.
• The parking brake is applied.
• Driver door opens (Driver door opens if doors are
attached or driver seatbelt is unbuckled if doors are
detached).
• The vehicle is driven greater than 20 mph (32 km/h) for
greater than 70 seconds.
• The vehicle is driven greater than 40 mph (64 km/h)
(HDC exits immediately).
• HDC detects excessive brake temperature.

 

[Tree Farmer]

But this can happen in any gear, HI or LO range. As I recall ABS is turned off when you enter LO range, but it happens just the same. My regular dealer is not good, and my Jeep is my regular driver. They're pretty clueless, and I'm not leaving it with them.
Other than this, and a couple of annoyances I've corrected using the Tazer device, this is the best Jeep I've ever owned. And I've had quite a few, having 4-wheeled all my life.
(Don't know why I'm shown as a "new member", been on here since 2020)

I'm really surprised that your post is the only place on the internet I've found reference to this problem. I've not talked to Jeep, because my dealer is also clueless. The commonality that I see is that we both have Tazer minis. I've never totally removed the Tazer, but you said that you have. There are reports of the Tazer causing other electrical problems. Have you talked to their technical support?

Oh, one other thing. The previous owner of my Jeep had a Tazer installed. It was gone when I bought the Jeep, but the extension wires were still there. The seatbelt ding and the TPM system were disabled. My guess is that someone at the dealership found the Tazer and removed it without reading the manual and doing it properly.

Thanks for replying to my post.

 

[XT Carol]

are you saying when driving in 2wd on a flat road, hill descent turns on? if so, you need to have the dealer look into that.
HD should not work in 2WD, only 4LO - from the owner's manual

Hill Descent Control (HDC) — If Equipped
HDC is intended for low speed off road driving while in
4WD Low Range. HDC maintains vehicle speed while
descending hills during various driving situations. HDC
controls vehicle speed by actively controlling the brakes.
HDC has three states:
1. Off (feature is not enabled and will not activate).
2. Enabled (feature is enabled and ready but activation
conditions are not met, or driver is actively overriding
with brake or throttle application).
3. Active (feature is enabled and actively controlling vehicle
speed).

HDC will be deactivated but remain available if any of the
following conditions occur:
• Driver overrides HDC set speed with throttle or brake
application.
• Vehicle speed exceeds 20 mph (32 km/h) but remains
below 40 mph (64 km/h).
• Vehicle is on a downhill grade of insufficient magnitude,
is on level ground or is on an uphill grade.
• Vehicle is shifted to park.

Disabling HDC
HDC will be deactivated and disabled if any of the
following conditions occur:
• The driver pushes the HDC switch.
• The driveline is shifted out of 4WD Low Range.
• The parking brake is applied.
• Driver door opens (Driver door opens if doors are
attached or driver seatbelt is unbuckled if doors are
detached).
• The vehicle is driven greater than 20 mph (32 km/h) for
greater than 70 seconds.
• The vehicle is driven greater than 40 mph (64 km/h)
(HDC exits immediately).
• HDC detects excessive brake temperature.

No, this problem is completely unrelated to Hill Descent. It is some component(?) actually throttling up the engine on downhills, causing the driver to have to apply braking force to slow the vehicle. Thus the brakes are having to work against the engine itself to slow, in addition to the hill.
To watch it happen, you need the center dash display set to show mpg. If you descend and the throttle is "closed" (full engine braking), mpg will read 99. If this problem begins, that number will change to lower mpg readout, because "something" is telling the engine to throttle up/accelerate. And it's NOT the driver's foot.

 

[cozdude]

No, this problem is completely unrelated to Hill Descent. It is some component(?) actually throttling up the engine on downhills, causing the driver to have to apply braking force to slow the vehicle. Thus the brakes are having to work against the engine itself to slow, in addition to the hill.
To watch it happen, you need the center dash display set to show mpg. If you descend and the throttle is "closed" (full engine braking), mpg will read 99. If this problem begins, that number will change to lower mpg readout, because "something" is telling the engine to throttle up/accelerate. And it's NOT the driver's foot.

Are you sure it’s just not the trans up shifting? Mine on some hills will drop to says 3rd or 4th gear while I brake. I will be off the brake letting it engine brake the rest of the decent and then it up shifts to say 6th,7th or even 8th depending on my speed.

 

[XT Carol]

Are you sure it’s just not the trans up shifting? Mine on some hills will drop to says 3rd or 4th gear while I brake. I will be off the brake letting it engine brake the rest of the decent and then it up shifts to say 6th,7th or even 8th depending on my speed.

No, friend, my mistake in not mentioning that important fact. This all takes place as I use the transmission in "manual" mode, thus locking it into an appropriate gear to descend the hill. Whether pavement or dirt. I can watch the 'mpg' monitor on the dash as we descend. When it's reading '99' I know I've got full engine compression braking. But inexplicably, if I continue watching, it often will begin (all on its own, no pedal input) to rise. It'll go from '99' to perhaps '18', and by then the driver is using some serious braking to slow the vehicle down. It's a crazy thing to experience!
When I first posted it several years ago, another Jeeper had experienced the same thing. Either it's a rare occurence, or people aren't very in-tune with their vehicle (possible, if you're not watching the mpg display), or it's only a few of our Jeeps malfunctioning in some way to cause it. I still don't know.
But yes, as I descend regardless of surface I'm usually controlling the tranny manually so it doesn't upshift as you've mentioned.

 

[bobfriesenhahn]

No, friend, my mistake in not mentioning that important fact. This all takes place as I use the transmission in "manual" mode, thus locking it into an appropriate gear to descend the hill. Whether pavement or dirt. I can watch the 'mpg' monitor on the dash as we descend. When it's reading '99' I know I've got full engine compression braking. But inexplicably, if I continue watching, it often will begin (all on its own, no pedal input) to rise. It'll go from '99' to perhaps '18', and by then the driver is using some serious braking to slow the vehicle down. It's a crazy thing to experience!
When I first posted it several years ago, another Jeeper had experienced the same thing. Either it's a rare occurence, or people aren't very in-tune with their vehicle (possible, if you're not watching the mpg display), or it's only a few of our Jeeps malfunctioning in some way to cause it. I still don't know.
But yes, as I descend regardless of surface I'm usually controlling the tranny manually so it doesn't upshift as you've mentioned.

Not related to hill descent control (because it's not enabled), but when I go down a long hill and am enjoying some engine braking to control descent rate, after a short while it is as if the transmission suddenly goes "free spooling" and the Jeep suddenly accelerates down hill due to gravity. This is for the 2.0L and auto transmission.

 

[jeeeep]

No, friend, my mistake in not mentioning that important fact. This all takes place as I use the transmission in "manual" mode, thus locking it into an appropriate gear to descend the hill. Whether pavement or dirt. I can watch the 'mpg' monitor on the dash as we descend. When it's reading '99' I know I've got full engine compression braking. But inexplicably, if I continue watching, it often will begin (all on its own, no pedal input) to rise. It'll go from '99' to perhaps '18', and by then the driver is using some serious braking to slow the vehicle down. It's a crazy thing to experience!
When I first posted it several years ago, another Jeeper had experienced the same thing. Either it's a rare occurence, or people aren't very in-tune with their vehicle (possible, if you're not watching the mpg display), or it's only a few of our Jeeps malfunctioning in some way to cause it. I still don't know.
But yes, as I descend regardless of surface I'm usually controlling the tranny manually so it doesn't upshift as you've mentioned.

where did you hear or read it would function like this, the mpg monitor is not an indicator of engine compression braking; you get the same reading if you were to put it in neutral and coast on a flat road.

Locking the gear in manual mode does not turn on engine compression braking on descent, since it's basically coasting (no brakes to control speed) it runs the transmission into higher RPM and as the Jeep exceeds the gear limit rpm's at some point you need to assist the transmission with the brakes.
Make me wonder if it's a self-protection to release the gear and coast - speeding up in the process since that's what it was doing anyways.

My old CJ would whine like a banshee before popping out of gear if I left it in gear to control downhill speed without applying the brakes, eventually you have to brake.

 

[XT Carol]

I'm really surprised that your post is the only place on the internet I've found reference to this problem. I've not talked to Jeep, because my dealer is also clueless. The commonality that I see is that we both have Tazer minis. I've never totally removed the Tazer, but you said that you have. There are reports of the Tazer causing other electrical problems. Have you talked to their technical support?

Oh, one other thing. The previous owner of my Jeep had a Tazer installed. It was gone when I bought the Jeep, but the extension wires were still there. The seatbelt ding and the TPM system were disabled. My guess is that someone at the dealership found the Tazer and removed it without reading the manual and doing it properly.

Thanks for replying to my post.

Now, that's a thought I'd not had--that the Tazer itself might be causing the problem. I'll have to remove it and take a test drive tomorrow, if I get the time. I can pretty easily replicate the descent problem, I'm so used to it, and I'm camped in high mountains so plenty of downgrades. And it's obvious from the dash gauge when it's happening. If I find it's Tazer-related, I will definitely reach out to its creator.

 

[XT Carol]

where did you hear or read it would function like this, the mpg monitor is not an indicator of engine compression braking; you get the same reading if you were to put it in neutral and coast on a flat road.

Locking the gear in manual mode does not turn on engine compression braking on descent, since it's basically coasting (no brakes to control speed) it runs the transmission into higher RPM and as the Jeep exceeds the gear limit rpm's at some point you need to assist the transmission with the brakes.
Make me wonder if it's a self-protection to release the gear and coast - speeding up in the process since that's what it was doing anyways.

My old CJ would whine like a banshee before popping out of gear if I left it in gear to control downhill speed without applying the brakes, eventually you have to brake.

Well, yes and no. In neutral and coasting I'd assume you'd get an "idle" reading for mpg, but I've never tried that. But it's not that as I descend the grade is so steep as to "pull" the engine into higher RPMs. The RPM is fairly low when it's holding back properly, I'd guess about 1,500. And the grade doesn't cause that to rise. What DOES is (as the mpg gauge drops a large amount) the RPM does rise. In fact, to a crazy point, 3K or faster. This is without touching the gas pedal. I don't let it go beyond that because by then my speed is too high to be safe. So I slow it down by fairly heavy braking.
I have let it go when the road allowed, and once the RPM was quite high (3,500+) it will often drop on its own. I can watch the mpg quickly rise too, back to the normal 99 it should read. It's a crazy experience, I notice people staring due to the engine RPM/noise. I don't let it over-rev often like that, there's no point.
So no, I don't see "self protection" as factoring in as the engine isn't laboring to hold the Jeep back and RPM isn't very high either.
I've wondered if at some point the computer sees the engine as "starving" for fuel and automatically adds throttle (and fuel) to correct what it sees as a problem?

 

[XT Carol]

Not related to hill descent control (because it's not enabled), but when I go down a long hill and am enjoying some engine braking to control descent rate, after a short while it is as if the transmission suddenly goes "free spooling" and the Jeep suddenly accelerates down hill due to gravity. This is for the 2.0L and auto transmission.

I just went outside to get a shot of the dash display that shows 'mpg', if I can include it. I don't know if your Jeep is the same as mine. In the picture, it's the orange part that's reading "0 Current" beside the fuel gauge. The Jeep is parked, not moving, engine at idle, thus the "0" mpg.
If you have a selectable display like that, it'd be interesting to see if your 'mpg' changes like mine does as you descend. To me, perfect engine "hold back" descending shows 99 mpg (no engine load/throttle closed), and moderate RPM of from 1,000 to about 2,000.

 

[XT Carol]

I just went outside to get a shot of the dash display that shows 'mpg', if I can include it. View attachment 428597I don't know if your Jeep is the same as mine. In the picture, it's the orange part that's reading "0 Current" beside the fuel gauge. The Jeep is parked, not moving, engine at idle, thus the "0" mpg.
If you have a selectable display like that, it'd be interesting to see if your 'mpg' changes like mine does as you descend. To me, perfect engine "hold back" descending shows 99 mpg (no engine load/throttle closed), and moderate RPM of from 1,000 to about 2,000.

And yes, I think the "free spooling" you're sensing could be this.

 

[XT Carol]

I'm really surprised that your post is the only place on the internet I've found reference to this problem. I've not talked to Jeep, because my dealer is also clueless. The commonality that I see is that we both have Tazer minis. I've never totally removed the Tazer, but you said that you have. There are reports of the Tazer causing other electrical problems. Have you talked to their technical support?

Oh, one other thing. The previous owner of my Jeep had a Tazer installed. It was gone when I bought the Jeep, but the extension wires were still there. The seatbelt ding and the TPM system were disabled. My guess is that someone at the dealership found the Tazer and removed it without reading the manual and doing it properly.

Thanks for replying to my post.

I looked back to where I first posted about this problem, 8-15-2021. As I re-read my post I mentioned that I'd experienced it before I ever had a Tazer, March of 2020, shortly after I bought the Jeep.
But I will try removing that Tazer, thank you.