I have a citroen AX 1100 F reg carburettor car with 80k on the clock. It's been running perfectly but all of a sudden it judders and doesn't pull away nicely when cold. Hesistates. I thought at first it was a fuel problem. But the car is converted for lpg and I seem to get the same problem on petrol or lpg. It does seem to clear when the car has got warm but stop for an hour and it will start doing it again when initially started for the first half a mile.
It also doesn't seem to idle nicely it seems to pulse.
Any suggestions where to start?