Citroen Xanita cuts-out

[blueted]

I've owned my Citroen Xantia 1.8 16v for around 3 years without problems until last month when I noticed the revs fluctuating while the engine was at idle. This problem was initially solved when I filled the tank but now it is back with a vengance! Whenever I take my foot off the pedal, once the revs drop off, the engine cuts out. In order to overcome this problem, I need to keep the revs above 20,000 but the moment it drops below this figure the engine dies.

There is no problem when driving, only when the car is slowing or stopped.

Could the electronic control unit be the problem?

Thanks.

[YvonneM]

My husband a motor mechanic says it is pulling in air. From the manifold, pipes or lots of places. He says to listen for hissing with the bonnet up and the engine running.