i have a '93 300d benz and every once in awhile when the engine is still cold the rpm would stop working when this occurs the a/c would not work properly and would be blowing warm air rather then the cold air it should be blowing in addition the engine isn't as powerful also it takes it much longer to get up to accel. but after about 20 or so mins the rpm would start to work and the engine would be more pwerful and the a/c would be real cold does anyone know what could cause this power loss i am completely clueless