general problems of the 2010 Kia Motor RIO

After driving to work approximately a 25 minutes to work I parked my vehicle and smelt something like burnt plastic. Assumed it was something in the area I work. After my shift roughly 8 hours I headed home and suddenly the car would not go more than 5 miles an hour then completely dead. After the tow trucked lifted the vehicle I was able to see severe melting of the undercarriage plastic. It could have been so much worse. It was towed to local kia dealership and have no idea to why yet this happened. This is an absolute danger to just happen to a well maintained vehicle randomly.

Since January my 2010 kia Rio has stalled at traffic stops. It usually starts again after several tries, although recently it needed a jump start. I've taken it to three mechanics who all say they can't find a code or what the problem is. I've tried gas additive, new crank shaft sensor, tune up. Nothing works. I've called kia customer service. There are no recalls but I still have a car I think is unsafe to drive. I've stalled in rush hour traffic on city streets and state roads several times. I have a case number with kia, and plan to take it to kia dealership in one more effort to find code or what's wrong. I don't have repair invoices handy but have spent more than $500.