Car: 1997 Mercury Sable V6 Vulcan Engine
My engine went bad, so I had an engine from a junkyard put in the car. This garage said I was to buy the engine, and they would install. I did so. The junkyard assured me that he knew the son of the guy who had the car the engine was in, and it was in good shape. Now that's it's in, it seems to me running nicely, but I just wanted to check one thing, because sometimes engines can break a piston ring if oil is not squirted into the engine through the spark plug hole and let to soak in if they have been left for many months.
Instead of buying a compression gauge, I decided to try a little trick I heard about way back. That is, as the engine is running, take off each spark plug wire and then reattach, one after the other.. If the engine seems to run rough visibly rougher when you take the spark plug wire off the cylinder, that means you are getting output from that cylinder and it is relatively alright. I did this for all six cylinders, and each time I took off the spark plug wire it ran visibly rougher and then ran noticeably better when reattached.
Am I safe in assuming that this quick-and-dirty test means that the cylinders of this used engine are in good shape?