My son just bought a 2007 Sonata with 2.4 motor. The motor turns over but its really slow and does not make the ruh, ruh, ruh noise. I checked the starter, good. Battery did have to be jumped off but charged to 100% and it turned over for a split second then just made the same slow crank as before. pulled serpentine belt off to ensure no added tension is on the motor during crank and still slow crank. It threw a cam shaft position sensor code, replaced sensor and still same issue. Any suggestions?