Problems with fuel I think Need help ASAP

[bumbl/e30/ownage]

Alright guys here's the scoop

I have a 1986 Bmw 325


The problem:
When I crank up the car it starts rpm's go to about 2K just as it goes up it goes right back down.

Sometimes it'll stay on but what it is doing it just cuts off.
Another as I was driving I would press gas and the car would jump forward and then slow down.

One more thing I can get it to stay on when after I crank the gas it will only stay on if I give it gas.(btw I have 3/4 a tank of gas) then sometimes it will stay on, on the second crank

Thanks

[bimmerboy08]

check to make sure your air filter isn't clogged, then I would say fuel filter after that.