I had this problem with our CGC70 and after changing the regulator and diaphram and still had the same problem. I contacted the dealer and I was told to change cap, rotor, and wires......then ignition coil with same results. I pulled the throttle body apart and found that enough of the LP honey had gotten pulled into the throttle body and down into the intake, partially plugging the intake ports.

As for checking the codes if there are any, with the ignition switch in the on position but not running pump the gas peddle 3 times. The check engine light will flash once, then twice and then any codes will flash.