Hello

I have a 2007 ford ranger 3.0 liter 2 wheel drive Sport

I notice when going up a hill steep or semi steep it some times the vehicle revs high at 5'000 rpm and stays in a lower gear for minutes then jolts the vehicle back to its proper gear the higher one and also when towing a light 1300lb trailer on a 10% hill it lacks total power I also noticed the check engine light flashed while going up hill then went away I have been told it drives flat or lazy

Thanks