I hope this can help others. My van would start and drive fine, but had no real pulling power. When I attached my caravan to go away, it struggled to pull with no torque and i had to use all the gears to make it move. It had been in various garages including main dealers. One dealer had it working for a couple of weeks, but none of them could seem to fix it permanenty. Recently had a new timing belt and water pump fitted, and the mechanic who I had also asked previously to find the fault rang me to say he has found the problem. It turns out there is a small metallic vacuum pipe attache to the rear of the rocker cover, this had come unclipped and had rubbed a hole through, but is nigh impossible to see during a normal inspection. See attached picture. I now have my pulling power back and hopefully my fuel consumption will be better.
