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No longer sure if I trust ACC

5K views 33 replies 17 participants last post by  comnjeep 
#1 ·
When I was first researching the Grand Cherokee, I was excited that it was available with Active Cruise Control and I was eager to give it a shot. I bought my 2012 Overland 5.7 in April and despite a few electronic glitches that would tell me ACC/FCW wasn't working (which disappeared when I restarted the car) I've been a pretty big fan of the system. It's not seamless, doesn't substitute for the driver's own judgment in most situations, but is nonetheless a nice feature to have. However, today it scared the crap out of me. Today I was in the middle lane of the interstate and had the ACC set at 74, distance 2, and had no cars close ahead of me. There was a Range Rover behind me (following much too closely, in my opinion). It had snowed earlier and was still a very windy day. A plastic shopping bag blew across the lane ahead of me, and my FCW went off and the car started the emergency braking which almost caused the car behind me to hit me. Without mentioning the fact that I looked like a complete idiot at the very best, this situation could have been bad. If some irritable person was behind me and thought I was stomping on the brakes to tell him to back off, that could have escalated (the FCW braking obviously isn't full power, but certainly enough to get your attention), and I swear if that Range had been following a foot or two closer, he could have hit me. I love the system but after this I'm very wary of using it again. Has anyone had a similar experience?
 
#2 ·
Not sure if the radar can differentiate between a shopping bag or a bowling ball or deer. In those cases it would be nice to get a head start on braking...
 
#3 ·
99% of the time, the system works just great, and does exactly what I'd expect of it. I've become used to the way it works, so I can often cancel it in anticipation of a false alert, speeding up/slowing down when it doesn't really need to, etc., but I certainly wasn't expecting a drifting plastic bag to set it off!
 
#5 ·
The salesman I'm working with is trying to talk me into the Advanced Technology Group. I agree with him that they are great features, but I believe they can lull someone into a false sense of security. Of course that's just my own personal opinion, and I also want to immerse myself in the driving experience and keep fully aware of my surroundings. In heavier traffic on interstates I'm even uncomfortable using cruise control. Just "old school" I suppose.
 
#11 ·
FCW isn't perfect-- I've noticed that it gets a bit scared of corners, particularly on nice windy roads we have here in Europe. But I've only had the ACC pull emergency braking on me once, and that was an idiot pulling in front of me on the autobahn without looking in his mirror-- so it did exactly what it was supposed to, exactly when it was.
 
#12 ·
FYI, the FCW does not apply the brakes (at least not on the 2012 JGC). The ACC system will apply up to a maximum of 25% of the vehicle’s braking capability


Forward Collision Warning — If Equipped

Forward Collision Warning (FCW) warns the driver of a
potential collision with the vehicle in front of you and
prompts the driver to take action in order to avoid the
collision.
FCW monitors the information from the forward looking
sensor as well as the Electronic Brake Controller (EBC),
wheel speed sensors, i.e., to calculate a probable rear-end
collision. When the system determines that a rear-end
collision is probable a warning message (both audible
and visual) will be displayed on the EVIC. When the
system determines a collision with the vehicle in front of
you is no longer probable, the warning message will be
deactivated.

ADAPTIVE CRUISE CONTROL (ACC) — IF
EQUIPPED


Adaptive Cruise Control (ACC) increases the driving
convenience provided by cruise control while traveling
on highways and major roadways. However, it is not a
safety system and not designed to prevent collisions.
ACC will allow you to keep cruise control engaged in
light to moderate traffic conditions without the constant
need to reset your cruise control. ACC utilizes a radar
sensor designed to detect a vehicle directly ahead of you.
NOTE:
• If the sensor does not detect a vehicle ahead of you,
ACC will maintain a fixed set speed.
• If the ACC sensor detects a vehicle ahead, ACC will
apply limited braking or acceleration (not to exceed
the original set speed) automatically to maintain a
preset following distance, while matching the speed of
the vehicle ahead.
 
#13 ·
While the braking by ACC was automatic, the same potential result would have been in place if you saw a problem and applied your brakes manually. The dude following too closely behind you was the problem, not the technology you were or were not using.

I was skeptical at first about ACC, but have come to love it. I occasionally get a "false" with FCW, but have never experienced ACC braking for something small like a bag blowing across the road. That's strange...
 
#15 ·
Have you tried changing the distance? Set to 1 or 2, and it'll only react much closer. I've noticed distance 3 can be annoying for that, reacting way too early to cars in front (like when I'm about to pull into the passing lane, and it decides to start breaking for the truck in the driving lane).
 
#16 ·
I agree with rovinrail...I started out at "3" when I got my Jeep, but quickly realized that I needed to move to "2" and now "1" for most circumstances. The only time the braking is annoying for me is when some idiot cuts in front from another lane and honestly, I'd have to be braking manually for that, too, in most cases as I really don't like following too closely.
 
#17 ·
I always leave it on the shortest distance. The braking I see are things like a car getting off the highway and is clearly on the exit ramp, yet my Jeep slams on the brakes. I usually counteract the braking with full throttle acceleration.
 
#20 ·
I'll also mention that I've gotten into the habit of wiping the radar sensor off with reasonable frequency, especially during these winter months with all the "stuff" they put on the road to counteract freezing. (sam for the backup camera lens) I seem to get very few "falsies" when the dome is clean.
 
#22 ·
Today I was in the middle lane of the interstate and had the ACC set at 74, distance 2, and had no cars close ahead of me...and my FCW went off and the car started the emergency braking which almost caused the car behind me to hit me.
Happened to me too just last week while tooling around at about 72 without anyone or anything in front of me. Suddenly it just slammed on the brakes for no reason. I immediately took control. Luckily the person behind me was a fair distance away, but I'm sure he was wondering "why in the world did that person just slam on the brakes?"
 
#28 ·
I know the FCW doesn't apply the brakes, and only alerts you, but I had the ACC set so it alerted me as well as applying the brakes at partial force. Since I posted, I've still been using the ACC and it works just like it always did, but I've got my feet much closer to the pedals just in case. In normal around-town driving, I've had just the FCW go off when a vehicle cut across in front of me at a similar distance. I'm assuming the bag was somehow inflated just enough by the wind for the sensor to recognize an object, and it floated directly across the lane, so the motion must have alerted the sensor.

I don't think ACC is a foolproof system at all, just a convenient aid in certain driving situations. On my daily commute, about 20 miles each direction, 99% highway, I probably turn the system on and off about 5 times in one trip, because I'm used to the way it reacts and I've learned what situations confuse it, and anticipate them.

As far as the system braking when a car is exiting but not fully in the exit lane, mine does the same thing. It makes you look like an idiot to fellow motorists, but the car is just waiting until the lane is completely clear before accelerating. Not ideal, but imagine the trouble they'd get into with a car accelerating before the lane is clear!

When I first got the car, I would usually use distance 2 or 3 (tailgaters are one of my pet peeves), until I realized that any distance greater than 1 is an invitation for people to cut you off.

Finally, the Rover behind me was a nice Sport Autobiography, so I do believe it was equipped with ACC. Being a Rover, I'm sure there was a wiring issue and it wasn't working at all. Another reason I'm glad I drive the American Range Rover, even if it does occasionally think I'm about to have a major collision with a grocery bag :D
 
#31 ·
I don't think ACC is a foolproof system at all, just a convenient aid in certain driving situations.
The problem with "foolproof" systems is that, as soon as one is developed, someone else goes and makes a better fool.

:slapfight:

The FCW and ACC systems are meant to be AIDS to an alert driver. Don't be a passenger who just happens to be sitting behind the steering wheel! Be in control of your vehicle and aware of your surroundings!

:thumbsup:
 
#34 ·
At least there will always be race tracks and off road trails for real car enthusiasts.

I just rented a ford escape last week. Nice car, nice little turbo engine (except like my last turbo engine it smells of oil when you turn it off)... The down side, the electronics: every time I was speeding it would alert me, and there was an 80mph max on the car. Personally, I think that's poor business practice to offer a car that can't go as fast as traffic or a stock version on a dealer's lot without telling the customer. I was overall impressed with the little thing though, even though I high-sided it in a snowy driveway with ease... Did I mention modern "AWD" cars that have no way to override the TC are totally useless? Basically all FWD based "AWD" cars I've driven are so useless in real traction situations because they cut power when a wheel slips. They're FWD until you need AWD, then they're dead in the water. Antoher example of electronics making life oh so much better...
 
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