Low Compression while engine is running
 

I have a 1995 Maxima and have a misfire on the number 5 cylinder (back driver side). I know the coil is good because I swapped it with another cylinder and still had a misfire on number 5. Nearly positive that the fuel injector is good because it was changed less than a year ago. Plug is good also. So fuel and spark is good.

That leaves compression. If I disconnect all the coils and just turn the engine over with the starter, number 5 cylinder has over 120 psi, which should be fine. However, If I reconnect all of the coils and have the engine running on the other 5 cylinders, number 5 cylinder only has 30 psi, which would cause the misfire.

I'm thinking I have a valve problem, maybe a weak spring or a sticky valve or something. If it was bad piston rings I wouldn't be getting the 120 psi when just cranking it with the starter.

Any advice/thoughts is greatly appreciated. Thanks.

Have you squirted a little oil into the spark plug hole and then rechecked it?

No but that does sound like a good idea. Thanks for the input