I've seen faulty throttle actuators cause symptoms like yours'. The motor that controls the throttle valve can't overcome the return spring tension quickly enough. Try holding the gas pedal down about halfway while the engine is cranking, then release it the instant the engine starts. If the problem goes away, the actuator is the likely cause. Of course, if you have access to SDS you can test the actuator via the "Actuations" menu choice. I've found many actuators that can lower the engine speed with no problem (due to the help of the return spring), but have trouble increasing RPM. Good luck