I'm not sure what to do.

Has anyone had this problem before?

If so or if not, can they give me any suggestions about how to fix it?

I followed the instructions in the manuel.

I pushed the cruise control button located on the left panel next to the steering wheel and a green light illuminated.

Then I drove to a desired speed above 30 mph and pressed the set cruise button I believe it is called.

A green light that says "cruise" shows on the dashboard close to the speedometer.

For some reason it won't keep the speed. It decelerates.

 

Is your car still under warranty? If so, take it to a dealer. It should be covered.

 

We purchased 2011 Hyundai Sonata SE last month. The first time we attempted to use the cruise control it would not maintain the set speed, it would slow down. Also, while going down hill the car would pick up speed. We took the car to the dealer today, 7-11-2011, and after test driving the car we were told "that's how it operates". Well, we know thats not true and was told by the dealer service dept that Hyundai knows there is a computer problem and is working on it. We were told we should call back every month to see if they have come up with a fix for the problem.
As I am writing this my wife is informing the dealer that we don't want the car! we spent $25,000 for a car with a defective cruise control that can't be fixed?
I'm looking into California's Lemon Law at the moment. I know for sure we won't be keeping this car!

 

So you came here to dig up a 4 year old thread about a 7 year old car just so you can bitch and moan? WOW! Welcome to the forum.

 

Take it to somebody who knows backside from hole in ground.. did they verify your recalls all up to date and done ??