Audi Repair: 2002 A4 1.9tdi idle, diesel filter, petrol engines

Question
QUESTION: Yesterday it started to idle at just under 1000rpm, I rang a friend of mine who is fairly handy and he said it could be injectors or the timing belt but hes not too familiar with audi. Is this going to be an expensive fix?

ANSWER: I don't understand the question or the problem, but if it the injectors are faulty then you'd expect rough running and a 'diesel knock' and if the timing is off then you'd see whitish smoke from the exhaust. and where exactly is the idling??

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QUESTION: What does a diesel knock sound like? The thing is though when the car is stopped but ticking over it judders almost like a misfire and another thing is when I drive hard there is a smell of exhaust in the car and the manifold gasket seems to be ok and the exhaust is perfect.

Answer

well it kinda sounds like a loud tapping, it depends n how many cylinders are 'knocking' sometimes there is more then one 'knocking'
think of it as the diesel equivalent of 'pinging' in petrol engines. basically the diesel blows instead of burning and produces a knock.

have you checked the basics?? sometimes the diesel filter gets clogged with water and can produce the misfire. check the owners manual for instructions on draining the water.