Mechanic said the PCV is bad. Drilled hole in oil cap to test vacuum, and there was no vacuum. I asked him why he didn't just plug the hose going into the PCV, he said he didn't know if that would diagnose the problem. 2009 Mini Cooper R56/L12 56K miles. Symptoms: Car starts right up without issue, Idle is very rough for a while then smooths out. Drive for a bit, stop and rough idle can come back. Rough enough to almost stall. When engine is stopped, car can make rapid, muted thumping sound for about 10 seconds or so (may not be related.) Error code P2187. So the question is, how to test to see if the PCV valve is stuck open causing this issue.