Idling problem/engine light and airbag light on

I have a 99 jeep cherokee sport 4.0 V6. I have a new battery and alternator but the other day, I started the vehicle with no problem, the engine and airbag lights came on and the engine began to idle erratically, and then died. If gas is given it will stay running but as soon as you let off it will die again. Can you tell me what I need to do to rectify this situation? Thanks.