940 running help

[clareehunt]

I am no expert and know very little but have a problem with our 940. On wet cold days it starts fine but is really reluctant to accelerate. You can put your foot fully down but it will not gain speed. Sometimes it will lurch into speed or you have to release the foot and re accelerate. Once it has gained heat in the engine it seems to be better. Does not idle well either when all this is happening. It goes fine and the fuel relays have been replaced recently but this problem is getting worse, although it has been wetter lately and I though it was just the damp getting in. Can anyone throw any light on this. It is an auto 940, no turbo, petrol and built 1994(M reg).
Grateful for any help.
Clare