hi folks just new on here so first of all hello

managed to wangle an omega 2 litre gls automatic the other day just for a bit of a project, its got a bit of a problem though, started off when you started the engine it would idle normally, go into gear and drive normally, but when you put it in park it would rev up slightly and then engine would cut out, then yesterday thought a would take it a bit of a drive so its not just sitting doin nothin, was driving normally untill I came back out of super market, started it up, went to put it into drive and engine cut out straight away, tried re starting and putting it into gear but everytime was the same, engine would just cut out straight away, left it for a while and then it went into gear and drove, not perfectly though, revs were up and down all time when idling, sorry for massive post but not got a clue what it could be, any help would be much appreciated....