My Sister has a v6 Montana Van. She loves the van and is in pain thinking it cannot be fixed. The Problem is misfiring once it gets to operating temperature. No check engine light. New wires, new plugs, fuel filter and pcv valve. Runs real cold. Transmission shifts automatically and manually except when engine is running rough. Have read other forums which speak of changing sensors. Is there a common sensor problem which would not show on the check engine light or sensor problem at all. I think this is a 2001 van. Thanks for any help. 
