Trying to help mother in law - lives in country, and doesn't have a trailer to haul the LT Cub 1554...the 2007 mower began running rough (loud - sounds like it is trying to throw a rod?) - oil is full, but she told me she got the mower "high centered" on occasion, and does use the mower to pull her up some steep hills (I'd estimate 45-degree elevations). I cleaned out the fuel filter - but am at loss as how to proceed (short of taking it into dealer)