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nondriver
New User
Sep 24, 2016, 12:56 PM
Post #1 of 6
(1498 views)
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I have a 2008 mazda tribute 2.3 72,000 miles.. 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??
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Sep 24, 2016, 1:14 PM
Post #2 of 6
(1494 views)
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Some engines would do that normally with a lot of moving parts and turbulence near oil fill caps, some might not.
Why would you do this to an engine at all? It doesn't indicate anything just yet especially if fine with cap back on and oil is filled to within range,
T
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Hammer Time
Ultimate Carjunky
/ Moderator
Sep 24, 2016, 1:21 PM
Post #3 of 6
(1490 views)
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No, it means stop taking the cap off with the engine running.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Sep 24, 2016, 1:33 PM
Post #4 of 6
(1487 views)
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It's up there with how does the car handle if I drive it with the wheels off! Why do this?
T
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Discretesignals
Ultimate Carjunky
/ Moderator
Sep 24, 2016, 2:12 PM
Post #5 of 6
(1480 views)
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The reason you feel air vibrating in and out of the hole when you take the filler cap off with the engine running is because of the air pressure changes inside the crankcase as the pistons are moving up and down. The reason the engine idles different is because you created a vacuum leak of sorts that is causing the MAF sensor to read less air entering the engine than it normally would. The engine controller will reduced some fuel pulse width injection because of the MAF's input. That causes the change in idle speed.
The best way to test PVC system is to install a vacuum gauge onto the dipstick tube. With the engine idling, the gauge should not register a vacuum or build positive pressure normally. If it builds a vacuum you have a restriction on the vent side of of the system. If it builds pressure, you might have non functioning PCV system or you have excessive blow by from ring problems that is overcoming the ability of the PCV system to vent the crankcase.
To check the function of the PCV system plug the ventilation hose that is attached to the intake ducting. With the engine idling, you should see a vacuum form on your gauge. That indicates that the PCV system is functioning. If it doesn't build vacuum when the ventilation hose is plugged off, that means you either have no vacuum from the intake manifold reaching the crankcase or you have air leaks from the valve covers, oil pan, seals, ect. It is possible to have lean codes from leaking engine gaskets believe it or not. That is where a smoke tester comes in handy.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Sep 24, 2016, 2:28 PM)
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nondriver
New User
Sep 24, 2016, 2:36 PM
Post #6 of 6
(1475 views)
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Thanks for your help..
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