It's had a new throttle body, so the reply doesn't seem relevent. I have tried tapping it. Why would it buzz?
The above salls either at idle or coming to a halt. It then refuses to start for some time. It cranks fine but doesn't start. It also often refuses to start after it has been used and parked up for a while. When you return to it it won't start. I keep trying it every few minutes until it starts. My local Citroen dealers has put a new throttle body on it and an O2 sensor. They made no difference. It has had a new fuel and air filter. I have notice that the idle control vavle? On the end of the throttle body make a continuous buzzing noise when it won't start. When stopping normally it buzzes and whirls for a short while like something is resetting.