88 Civic - Bad Cylinder? Any other ideas?
 

265,000 miles on engine, just stalled one day, able to get home but had to keep the RPMs above 2000 to prevent stalling and had mild smoke coming out tail pipe. Has an audible knock. Cleaned plugs and when pulling the wires one at a time while running, engine sounds worse vs remaining the same to indicate a bad plug/wire. Compression = 100, 80, 80, 75 while cranking and 140, 140, 115, 105 while idling. Pulled cover while running and see nothing obvious. Any thoughts?