Recreational Vehicle Lpg Tank Valve/gauge problems of the 2013 Chevrolet Sonic

While driving my car for the past year now I have noticed my rpm gauge sticking and revving on its own. It is starting to happen more consistently. When I'm driving downhill the rpm gauge will rev high and stay stuck high. Then when I put the car in park it will rev high on its own and stay stuck and eventually come back down. Something new I have started to experience is when I'm at a complete stop the rpm gauge will start revving up and down on it's own while my car lights brighten and dim and my warning light comes on that I'm sliding which is impossible since I'm at a complete stop. I have also noticed the transmission has started to feel jerky lately with everything else. I just purchased this vehicle almost 2 years ago and I only have 58,000 miles on it.

While driving home from work doing 55 mph the car just suddenly turned itself off with no warning. The dashboard went blank. Was able to pull over off the road. The key was still in the on position. The car restarted with no problem but my gas gauge showed only 1 bar and the miles per tank showed 40. Before the incident I had 1/2 a tank of gas. As I started driving again the gas gauge little by little started to move back up to where it was. Very scary.