I have purchased the sonata 2003 V6 GLS, after 1000 mills the car started experiencing loss of power and when going up hill in third gear around 30-35 mills per hour, loss of RPM and power, adding gas would not result in addition of RPM and power, the car would increase speed slowly and when reached to around 40-45 mills per hour the RPM would suddenly go height, still in third gear, then switched to fourth gear. In addition spars have black carbon deposit on the inside of the plug, not on the conductor and insulator. Recently the car is bucking on the highway every now and then. Went to two dealers, computer does not show any code and they are dismissing all this as something being wrong with the car. ANY IDEA?
Thanks.
Eli