What Happened?? Bug in Hill Decent Control?

[bradyh20]

So I put my Raptor through it's paces today up on Cajon Plateau in Southern California.

The Raptor ran strong and smooth. We had a total blast.

There was one point, though, when the Raptor turned itself off. Let me describe the situation:

We had just finished doing some doughnuts a short distance away (about a minute prior), and there was a very steep run going up the side of a hill. I decided to have a go, so I drove over, stopped at the base, and started to go up slowly. A few feet up the hill, I decided that using four wheel drive would be better, so I stopped, and decided to check out the Hill Decent Control.

So this may be a case of 100% user error, and the Raptor was designed to turn off, but here's what happened. (I know this cause I have it all on video).

I left the truck in drive, and hit the Hill Decent Control button. The computer indicated that Hill Decent was active, so I let off the brakes. The truck started to roll backwards, the brakes pumped once, the oil icon showed up on the dash, and the truck turned itself off. Keep in mind, the truck was still in drive.

I backed down the hill without power (yikes), and put a nice sized gouge in the rear quarter panel, but once back on flat ground I put it in drive and it started up fine.

I'm very glad there was no permanent damage to the Raptor, but I'm also wondering what the heck happened. Should the truck turn itself off in that situation?

If Hill Decent hadn't been active, I imagine the truck just wouldn't have moved (try it). Anyways, I'm super happy with the truck. I may forward the video to Ford SVT for them to take a look at in case it is something that could be fixed.

Now to my text quest: how much for touch-up paint lol....

 

[MarkT]

Nothing wrong with hill descent.

The problem was that you can't roll backwards in "drive" very far at all without stalling the engine. It's not a "fault"... just the way it is. Next time select "reverse" when you want to back down a hill and the engine will stay running.

The amazing thing I found is that hill descent works just fine even after the engine stalls... as long as you don't turn off the key or something.

(I did the same thing myself... except for the damage... ouch! that sucks.)

 

[bradyh20]

Thanks for the reply MarkT...

Yea, I feel a little stupid even posting it, but I figure it'll either make me better or the truck better. Sounds like it'll be me this time. =D

 

[BigJ]

Wow! Sucks that happened, but awesome that you caught it on video. Seriously chase out your idea of getting it into SVTs hands. They've seemed to be really interested in how these trucks are performing in the real world. I imagine they'd be all over your experience.

Without having seen the video, I'd guess the truck stalled. I wouldn't so much call it "turned itself off" as I'd say the load on the motor was too much for the system to cope with, and it bogged to the point of stalling.

Do I understand you correctly when you say you were going to try and back down the hill in Hill Descent mode? You had it in Drive when it stalled?

If so, it kinda makes sense to me... the system detected you were in Drive (meaning you wanted to go forward) but that you started to go backward, it tried to stop the backward movement, and maybe (total speculation here) the brakes were on when it tried to accelerate... the weight of the truck moving down hill combined with the force of the brakes on was too much for the low RPM and it stalled.

Keep us updated. Very very interested to see if SVT has any thoughts on this.

 

[MarkT]

I've played with hill descent and it *never* applies engine power to maintain speed. I was hoping it would, but it doesn't.

It uses gravity for "power" and the ABS braking system to keep the speed down. And it's not a "hill holder" in that it will keep you from rolling completely. In other words, it keeps the truck from exceeding a set speed but it won't stop the truck from going slower if the hill isn't steep enough to maintain the set speed. And it's designed to work when backing down a hill... but to keep the engine running you need to select reverse when backing up.

 

[bradyh20]

The part that I don't understand, then, is that when I don't have it turned on, it is a "hill holder." There's a good grade on the road leading to my condo. When I stop at the stop sign, I can let my foot off the brake, and the truck will stay still until I hit the gas pedal.

I guess the Hill Descent Control doesn't do that. No biggie, now I know.

 

[MagicMtnDan]

The part that I don't understand, then, is that when I don't have it turned on, it is a "hill holder." There's a good grade on the road leading to my condo. When I stop at the stop sign, I can let my foot off the brake, and the truck will stay still until I hit the gas pedal.

I guess the Hill Descent Control doesn't do that. No biggie, now I know.

Huh?

Let me see if I got this correct, when you're in drive going up the hill and you stop at the stop sign and then you take your foot off the brake and the truck will stay where it is until you hit the gas pedal. Is that right?

There is no "hill-holder" on an automatic transmission that I know of. There is a hill-holder feature in some manual transmissions (new BMW manual transmissions have it - they briefly will hold the vehicle from rolling backwards after you've let out the clutch while your right foot is moving from the brake pedal to the gas pedal).

It sounds like you're talking about the truck's idle speed (under 1,000 RPM) holding the truck from moving backwards before you press on the gas to go forward (while in drive). If your truck doesn't roll backwards then you're not on a very steep hill since idle power is not enough to hold the truck in that spot on a steep hill.

 

[bradyh20]

I don't know what mechanically is going on, but I know for certain what happens. I let off the brakes, truck doesn't move till I hit the gas.

I even showed my girlfriend how cool it was because I figured Ford did it on purpose. It's a pretty steep hill, too...

 

[MagicMtnDan]

Brady, I think it's simply your truck idling in Drive. Are you doing anything else (pushing any buttons, dragging your feet etc.)?

 

[bradyh20]

Lol, nope... I tried it again on my way home and it worked again. I guess the truck makes more power at idle than I'd figured.

Cool!!