My wife's Yaris stalls when stopped at lights after first juddering.

Also when she accelerates, whether on a highway or after slowing down around a bend, the car completely loses power and sometimes the exhaust "POPS". One 1 occassion it failed toaccelerate from a standstill after pulling over at the side of the road for a few minutes with the engine running.

The problem only seems to occur after the car has been running for a while, it's fine first thing in the morning.