Recreational Vehicle Lpg Tank Valve/gauge problems of the 2012 Hyundai Sonata

I'm not sure if this is an engine problem. When I would take off in my car, I accelerate and after I started going, I could push the pedal all the way to the floor and it had no power, it would almost completely stall in the road. I let off gas and push again and it would regain power and drive. No check engine light came on, no low oil, no service lights at all. All of the gauges in the dash red great and everything was normal. I started my car one day and it started making this chirping noise, almost like a bird chirping when I accelerate, but once I got up in speed the chirping stopped. I then started my car and there was a clicking, ticking type noise that got worse after 2 days. I took the car to a shop and was told it needed a new engine. Again, all gauges are completely normal, no check engine light at all to warn me there might be a problem with my car and now it cant be driven. I purchased this vehicle new. Why doesnt the check engine light or gauges work to warn of possible issues, this has to he a defect and what is the chirping, stalling, loss of power? if my engine was going bad, why did the system fail to alert me?.