Question

2001 BMW X5 with the engine code P1340 and intermittent smoke. What could be the problem?

Answer 1

P1340 Misfire

This is a random misfire condition. what possible cause for this would be the PCV system or what is referred to in BMW as the pressure control valve, it can cause the misfire with the intermittent smoke (as in alot) with the engine at idle

Answer 2

P1340 BMW Code - Multiple Cylinder Misfire During Start
Read more: https://www.autocodes.com/p1340_bmw.html