yeah this is a common problem with these carbs TRD_07, take the airfilter casing off, this will give you a better view of the carb. Looking from the front of the car towards the carb, you will see on the front left handside an alloy diaphram casing that is part of the carb, it has a vacuum line coming off it and going to a vacuum tree in the coolant outlet, when you find this one vacuum line just put a ball bearing in it. what happens is due to emission requirements under some conditions this diaphram opens an enrichens the mixture, when the carbs are old it opens at idle and floods the motor causing stalling. You will notice that your car starts immediately and puffs a small amount of smoke and then runs fine. I actually have a sprinter in the workshop now but don't have a digital camera! or I would take a picture, basically it's easy to find as it's the only part at the front of the carb(ie facing towards the radiator) with a vacuum line coming off it. Hope this helps, if it doesn't let me know and I'll try and get a picture for you.