The engine rumbles randomly while idling or stopped at a light. This happens around 700 RPMs where it fluctuates up and down on the RPM meter. At this point, the engine makes a rumbling noise. All of the spark plugs were just replaced and one of the ignition coils, due to a crack. I also have white smoke coming from my exhaust, which I think is associated with the crankcase oil separator valve.
It sounds like you may be getting oil into the combustion chambers of your engine causing it to burn off in the exhaust. This is the white smoke you see. This may also be related to your idle issue as well because a burning oil explosion and a burning gasoline explosion will cause the engine to react differently. If oil gets into the combustion chambers for too long the spark plugs may be fouled out by the oil and require replacement again. If the crankcase oil separator valve is the part you suspect, I would recommend having a professional, such as one from YourMechanic, come to inspect that part and any others related to it. A repair of your problem can ensue once a few parts have been inspected for faults.