quarter48

When the engine revs up over 2000 rpm or has a load applied to it the engine will start knocking. Ran compression check, cyl #1, 3 and 4 have 160-170 psi, cyl #2 has 0 psi. Timming chain is tight. Pulled head, valves appear to be seated correctly, head gasket looks OK (no trails), piston is tight (no side movement), no marks on cyl wall (broken ring). Also when engine was running it had a lot of vacumm in valve cover when opening oil fill cap. Hope someone can give me some ideas on what to look for. Thank you.

FixUrNissan

Did you send the cyl head out and check for cracks?

BoOCh_nse

4 cyl engines do have pressue and vacuum in the crank case unlike 6 and 8 cyl because of the delay between pistons moving up and down. a piece of paper should be both pulled in and pushed out. check the pcv valve, it may be stuck open slightly if the paper is constantly sucked in. as far as your compression issue somethings very wrong. it should at least have some compression if everything you say is true. retry it but this time put three squirts of oil in the spark plug hole before you test. if this greatly improves the compression, the rings are bad regaurdless of how they look. check out the valve springs on that cyl too. it is also possible that one of the valves are sticking in the guide.