Adaptive Cruise Control (ACC) issue -
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post #1 of 7 Old 09-18-2019, 12:36 AM Thread Starter
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Adaptive Cruise Control (ACC) issue

Hi folks. Have. A new 2019 GC Limited X and now has 5200 km on it. When I engage ACC or regular CC, I notice that the speed is not smooth. Even when on level roads or no one in front, I can feel a very slight pressure on my back like the speed is pulsing.

To illustrate better, and be more exaggerative, it would be like feeling the car bounce between two speeds. But this sensation I am feeling is very slight but definitely noticeable. It’s not at all like any other ACC/CC that I’ve used. The speedometer does not look like it’s moving but I can see MPG changes so I do think that it’s revving. Again, very slight but also annoying.

I recently had a rental car and drove a 2019 Dodge Charger, and it was just normal. It hugged the set speed perfectly.

Anyone have this issue? What is the fix?

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post #2 of 7 Old 09-18-2019, 04:54 AM
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What did the dealership tell you when you took it in, since it's obviously still under warranty? They'll be able to best diagnose it and it won't cost you anything.

If the RPMs are changing, speedometer is not changing and it feels like it's shifting, that's probably what it is. That Jeep has an 8-speed transmission. At highway speeds, there is very little difference in the overdrive gears and they are known to up/down shift a lot.

'09 JK Rubicon
'01 XJ Sport
'10 Fusion
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post #3 of 7 Old 09-20-2019, 01:16 PM
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2014 WK 
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I think I know what you are talking about, I've experienced this once or twice with my vehicle but my vehicle was in snow-mode driving on wet and slushy roads. It felt like it was accelerating and slowing down, accelerating and slowing down, etc. but it didn't have an affect on my speed as my speed was stable while using the cruise. Its possible it could be terrain related (in my case), but i think it did it also when the roads were wet (and still in snow mode) and that's why I bring it up. Haven't experienced it since so I never brought it to my dealers attention. Does it do it all the time on any road and any select-terrain setting?

2014 Jeep Grand Cherokee Summit 4x4 3.6L V6.
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post #4 of 7 Old 09-20-2019, 02:50 PM
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2011 WK 
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Location: New England
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V6 or V8? The WK2 gear ratios are a bit different than the charger, but it should be smooth. But smooth is subjective and you may be more sensitive than others. I’m thinking a little more throttle than expected is needed to maintain speed and the transmission downshifts to a better power range, when the target speed is reached the throttle closes a bit and it upshifts. So anything that effects engine performance, like a vacuum leak or dragging brakes, low tires, or drive line drag, as in snow mode, will push it over the shift point. I’ve noticed the cruise control has a tendency to use engine braking instead of the brakes where it can.

Dunno if a dealer would find anything, the best approach may be to drive a similar WK2 under similar conditions and compare.

I have reached the age where all compliments will be followed by “for your age.”
Current: 2011 Grand Cherokee Overland V8, 2009 Liberty Rocky Mt V6
Previous: 2000 Grand Cherokee Laredo I6, 1979 CJ7 I6 Quadratrac
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post #5 of 7 Old 09-20-2019, 11:57 PM Thread Starter
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I have not yet taken to dealer but that’s happening tomorrow. This is a V6 engine and the driving mode is normal. And the roads were dry. The terrain was relatively smooth.

I agree that I could drive another 2019 GJC V6 and take the same route and see if it has the same feeling. I will ask the shop foreman to go with to see if he can sense what I am trying to get across.

I am not sure if the sensor or camera is properly aligned or if the cruise control needs to be recalibrated.
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post #6 of 7 Old 09-22-2019, 09:47 AM
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I use my ACC all the time and it is smooth as butter in a straightaway with nothing in front of radar. Definitely seems like yours is operating incorrectly.

2000 TJ Sahara (sold)
2015 Grand Cherokee Summit - 6 cylinder Gas
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post #7 of 7 Old 09-26-2019, 12:42 AM
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Location: North DFW, Tx
Posts: 141
Same for me as Tampamark. Works like a champ.

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