I just finished changing out engines in my vehicle. I have a 1994 ford ranger with a manual transmision and 2.3L engine in it. After finishing installing the motor and reattaching all the wiring harnesses and vacume lines I'm able to start the motor and drive it in first gear but soon as I shift into 2nd gear the motor seems to just bog out or cease to run until it returns to a lower rpm. what could be wrong?