I have a 2008 tribute.. when motor is running I take off oil fill cap .. there a lot of air flow with sound coming out of fill hole.. like it an exhaust port lol... does this mean my PVC valve is clog??? also engine idles differently when cap is off??

 

Pressurized air normally gets into the engine past the piston rings. Some air will always go past the rings which is what the PCV valve is for; to vent that air.

PCV valve hole is fairly small...it can only release so much air...it may be plugged, but if you've got "a lot" of air coming out the oil cap hole, then you've got a lot of air getting past the piston rings...that is not good. If there's no smoke at the tail pipe, then your oil rings are ok, but the compression ring(s) are shot.

Different idle when you take off the oil cap along with "exhaust port" amount of air blowing out...bad compression rings is what I'm going with although it could also be a blown head gasket, but then you would also mostly likely have some type of coolant issue.

An auto parts store will loan you a compression checker. Easy to use, remove a spark plug, screw in tester, crank engine (need to make sure engine won't start) and write down the reading for each cylinder. Guarantee you at least one will have poor compression compared to the others.

There are videos at youtube that will give you better details on how to perform a compression check than what I gave here.

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