P0455 Hyundai -slight miss and loss of power

Question

After I am up to speed I only feel a slight miss in the engine but when I start up an incline, my power decreases and I have to downshift. Also have more noticeable miss when I first start out and upshift through the gears

Answer 1

This code is for a large leak in the evap system. This is usually caused by either a bad fuel cap, vent control valve or 

a sticking purge control solenoid. More often then not the vent control valve sticks open and allows for the large leak. 

You can remove the vent control valve, add power and ground and listen for it clicking. If you don't hear any noise it's 

no good and should be replaced.

With the symptoms you are describing, I would check for a blocked converter.