Cruise control won't hold speed

[Gold Z]

On my 3.8 the cruise control varies by as much as 3 mph faster or slower than the set speed. My dealer is no help. Does anyone else have this problem?

 

[Mark_888]

Is that on a falt stretch of road, or when there are some inclines and declines in the road?

 

[Gold Z]

It's fine on flat roads. It only does it on slight hills.

 

[sandy]

there is another thread on this topic...search for cruise control

 

[EdVoylesHyundai]

It's fine on flat roads. It only does it on slight hills.

Page 5-28 of your owner's manual states that the cruise should only be used on roads with less than a 6% grade. That would seem like a "slight incline". 6% is different than 6deg. A 6% grade means that the road level rises (or falls) 6ft vertically for every 100ft of horizontal distance (100.1798ft of road travel). As you can see this is a very small angle, roughly 3.4 degrees. The manual also states that the car may speed up or slow down on larger inclines. It sounds like your system is working as intended. I hope this helps.

 

[Mark_888]

Page 5-28 of your owner's manual states that the cruise should only be used on roads with less than a 6% grade. That would seem like a "slight incline". 6% is different than 6deg. A 6% grade means that the road level rises (or falls) 6ft vertically for every 100ft of horizontal distance (100.1798ft of road travel). As you can see this is a very small angle, roughly 3.4 degrees. The manual also states that the car may speed up or slow down on larger inclines. It sounds like your system is working as intended. I hope this helps.

There is not much difference between 6% and 6 degrees because there are 90 degrees in a right angle. 6 degrees is 6.66% angle.

Having previously lived in Colorado where I frequently drove on I-70 through the nearby mountains across the continental divide, I can tell you that 6% is fairly steep (they post warning signs of declines that steep).

I suspect that Gold Z is experiencing this on much smaller hills than 6%, probably 1-3% and plus or minus 3 mph is a much wider range than on my old Toyota Camry, but that does not mean that the Genesis cruise control is broken (that may be the best that can be achieved with the current design).

I haven’t tried my cruise control yet because my Genesis is less than a week old and the break-in instructions suggest not running at the same rpm for prolonged periods.

 

[Gimli]

There is not much difference between 6% and 6 degrees because there are 90 degrees in a right angle. 6 degrees is 6.66% angle.

Not quite. A 100% incline (for example, 100 foot drop over 100 foot of horizontal travel) is a 45 degree angle.

 

[BigElm]

Regardless... I believe it's normal behavior as EVERY car I've owned would never be consistant on inclines or declines. The computer is continuously trying to calibrate exact speed while fighting with law of physics!

 

[Gold Z]

This is not normal. This is the only car I have owned in the last ten years or more that had this problem. My XL350L did not have this problem.

 

[Calvin]

It probably does not help that the Genesis has a low wind resistance and a very efficient drive train. Since the system does not apply brakes it has to depend on these things to slow the car down. I have noticed that this car "coasts" much more than any other car I have owned. I would assume that this efficiency makes it more difficult to slow the car down on a steeper grade even when the system shuts down all fuel to the engine. On the plus side, the gas mileage is helped by this a whole lot!

I believe that Volvo now has a cruise control system that applies the brakes but only to avoid an impact.

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[Poopsicle]

I used to drive a Chevy truck and the cruise control did the same thing. It even changed on windy conditions. My friend's Chrysler 300 unexpectedly gained 5 mph!!! and there was a cop right by us!

 

[Mark_888]

I have noticed that this car "coasts" much more than any other car I have owned.

I noticed this also, but wasn't sure if it was my imagination. My default driver information is set to show the current MPG and with careful driving it seems that one can achieve good gas mileage with the Genesis (if the display is accurate).

Of course, we are comparing various automatic transmissions. Years ago when I lived in Denver and was coming back from the mountains on I-70 into the city driving a stick shift, I could coast in neutral for at least 5 miles.

 

[Mark_888]

Not quite. A 100% incline (for example, 100 foot drop over 100 foot of horizontal travel) is a 45 degree angle.

What??? When I talked to the salesman about the Genesis, he specifically promised me that there was no math required to drive the car!!!

But seriously, my apologies to EdVoylesHyundai if his post was correct (I am still not sure who is correct or even if the Users Manual is correct), but when I have seen 6% grade warning signs in Colorado, the road is very steep and no one would expect a cruise control to work well at that grade.

 

[EdVoylesHyundai]

No worries, Mark. I looked it up here Wikipedia and just did the math. I could be wrong. What got me thinking was the pic on the right side of the page with the angle vs grade numbers.

I grew up in Central Texas and live in Atlanta now, so grade signs are foreign to me. I don't have any first-hand experience with labeled graded roads, so I am just doing the calculations and trying to visualize based on the results.

 

[EdVoylesHyundai]

On my 3.8 the cruise control varies by as much as 3 mph faster or slower than the set speed. My dealer is no help. Does anyone else have this problem?

Have you had a technician or service advisor ride with you (or drive with you riding) to witness the variance?

 

[Gold Z]

The tech took it out by himself. Said he could not duplicate the problem.

 

[CanukV6]

I have experienced this same issue. It is noticably worse that other cars I have driven, foreign or domestic. Its Ok on level road but any incline will cause the speed to drop off before the system starts to compensate. This ought to be a calibration issue that could be fixed with a firmware upgrade, but is probably beyond the Dealer level and will require a TSB from Hyundai.

 

[Gimli]

I have experienced this same issue. It is noticably worse that other cars I have driven, foreign or domestic. Its Ok on level road but any incline will cause the speed to drop off before the system starts to compensate. This ought to be a calibration issue that could be fixed with a firmware upgrade, but is probably beyond the Dealer level and will require a TSB from Hyundai.

One thing I would ask is: how heavy were those other cars you're comparing against? The Genesis is fairly heavy at 4k lbs and that will have a effect on just how well the cruise control can hold speed on inclined roads.

 

[Mark_888]

One thing I would ask is: how heavy were those other cars you're comparing against? The Genesis is fairly heavy at 4k lbs and that will have a effect on just how well the cruise control can hold speed on inclined roads.

From a horsepower to weight ratio perspective, even the V6 Genesis ranks higher than the majority of cars.

 

[Gold Z]

One thing I would ask is: how heavy were those other cars you're comparing against? The Genesis is fairly heavy at 4k lbs and that will have a effect on just how well the cruise control can hold speed on inclined roads.

It's no heavier than any other luxury car and they don't have this problem.