When I turn on the heater or air conditioning the engine pulses

Adding refrigerant with out knowing the exact charge in the system is fraught with danger, the system must be evacuated using a discharge machine and not allowed to escape to the atmosphere. With the system empty you first need to vac down the system and ensure that there are no leaks, conversely you should pressurise the system with comp air and also check for leaks, (a pressure leak may seal as a vacuum leak and visa versa) as you have had the need to add refrigerant there must be a leak in the system, and this should be rectified first. With the integrity of the system confirmed, the correct weight of refrigerant can be added, this should be done with a A/C charging station which can accurately weigh the refrigerant that is added to the system.