Hi,

When I start my 96 XJR6 during cold weather it starts fine and I drive off from home in my usual direction and come to a traffic light where I frequently have to stop. I have noticed that the engine's revs oscillate up and down at this point. This is felt by passengers in the cabin. Once the car heats up there is no problem.

What might cause this and is there any cure?

Cheers,
Nick

 

I've seen variations on this problem caused by leaks in the intake tract such as vacuum leaks or tears in the intake tubing near the MAF sensor. Check in that area to see if air's going where it shouldn't.