Volvo Repair: Volvo 850 irregular idle, proper diagnosis, volvo 850

Question
Hi,

I have a 1996 Volvo 850 Turbo with 160,000 miles on it and I am noticing that it has an irregular idle when I first put it into gear. It idles fine in Park but as soon as I put into Reverse or Drive it idles between 1000 and 700 RPM. Can you tell me why this is?

One other thing, i just bought this car and would like to know if the timing belt needs to be replaced. Is there an easy way to tell if it is time to replace the timing belt?

Thanks for your help.  

Answer
the idle could be a problem with the throttle body being dirty or a problem with the idle speed motr.it wil need to be looked at for a proper diagnosis.

there may be a silver sticker under the hood possibly on the timing belt cover that will say when it was done.it should be done every 70k miles.if any doubt replace it.if it breaks it will cost 3500 dollars to fix it as the head will be damaged.