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did you know a bad PCV valve can reduce
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your engine's efficiency by up to
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15% and cause your fuel consumption to
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spike by as much as 20% yeah you heard
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right that tiny often overlooked valve
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can quietly sabotage your engine
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performance burn through your gas and
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even trigger that dreaded check engine
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light when this tiny part goes bad it
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can cause everything from rough idles
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and misfires to full-blown engine damage
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in this video we are going to break down
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the most common bad PCV valve symptoms
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and showing you how to maintain your PCV
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system like a pro first let's discuss
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the function of PCV valve the PCV valve
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acts like a pressure release for your
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engine whenever your engine runs it
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generates tiny amounts of unburned fuel
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and combustion byproducts commonly known
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as blowby gases these gases sneak past
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the piston rings and build up inside the
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crank case the PCV valve allows these
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harmful gases to escape the crankase and
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reroutes them back into the intake
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manifold where they get burned off
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properly during combustion now let's
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discuss the symptoms of a bad PCV valve
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one rough idle or stalling one of the
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most noticeable symptoms of a bad PCV
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valve is a rough idle or unexpected
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engine stalling this usually happens
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when the valve gets stuck in the open
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position which may allow too much air to
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enter the intake manifold this extra
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unmetered air creates a vacuum leak that
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disrupts the proper air to fuel ratio
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and cause poor combustion as a result
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your engine may struggle to maintain a
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consistent idle it coughs sputters and
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sometimes even shuts down altogether
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you'll notice it when the car vibrates
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at idle or struggles to stay running
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when you slow down this issue is more
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noticeable in traffic or when idling at
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red lights two check engine light when
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the PCB valve goes bad it throws off the
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entire balance of the air fuel ratio a
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stuck open or closed PCV valve may allow
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too much or too low air to enter the
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combustion chamber when the engine's
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computer detects irregularities in the
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air fuel mixture and thinks the engine
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is running rich or lean it triggers the
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check engine light to alert the driver
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the ECM may also trigger a specific PCV
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related code such as P
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03000 even if the car seems to drive
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fine ignoring this warning could lead to
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more serious problems a scan tool or a
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visit to a mechanic can help pinpoint
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the issue quickly three increased oil
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consumption a bad PCV valve may turn
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your car into an oil guzzler if you find
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yourself topping off your engine oil
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more often than usual a bad PCV valve
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might be to blame a clogged or stuck
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closed valve causes excess pressure to
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build up in the crankcase this pressure
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can force engine oil past seals and
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gaskets into the combustion chamber or
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external areas of the engine as a result
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oil either gets burned off or leaks out
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leading to noticeable drops in oil
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levels this doesn't just mean more
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frequent oil changes it can also
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increase emissions and reduce engine
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efficiency four oil leaks another clear
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symptom of a malfunctioning PCV valve is
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oil leaking from the engine when the
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valve fails to release pressure from the
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crank case that pressure has to go
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somewhere and usually it finds the
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weakest seals and gaskets you might
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notice oil stains on your driveway or
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around the engine bay especially near
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the valve cover oil pan or rear main
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seal these leaks aren't just messy they
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can lead to costly repairs if the
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gaskets blow completely on top of that a
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leaky engine can pose a fire hazard if
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the oil hits hot components five poor
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fuel economy fuel efficiency takes a hit
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when the PCV valve isn't functioning
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correctly a stuck open valve allows too
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much air to enter the intake manifold
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which can make the engine run lean in
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response the ECU might inject more fuel
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than necessary to compensate for the
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imbalance on the other hand a stuck
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closed valve can cause a rich condition
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burning more fuel than required either
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way your car will use more gas to
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perform the same task over time this
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inefficient combustion can also damage
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oxygen sensors and the catalytic
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converter six whistling or hissing
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noises ever hear a faint whistle or hiss
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when your engine's running that sound
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might be a PCV valve struggling to
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breathe when the valve or one of its
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hoses cracks loosens or fails internally
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it disrupts the normal air flow and
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creates a vacuum leak that vacuum leak
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causes air to rush into places it
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shouldn't often making a high-pitched
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hiss that gets louder with engine speed
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these sounds are often most noticeable
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when the engine is idling or under light
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throttle seven black or blue smoke from
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the exhaust when the PCV valve is stuck
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closed the crankcase pressure builds up
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and forces oil past rings or valve seals
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into the cylinders where it burns along
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with air fuel mixture this results in
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thick black or bluish smoke exiting the
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exhaust pipe especially during
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acceleration the blue tint usually
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indicates burning oil while black smoke
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points to a rich fuel mixture both of
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which can be PCB related aside from the
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visual symptoms you may notice a burning
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oil smell as well eight sludge buildup
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sludge is a thick tar-like residue that
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forms when moisture blowby gases and
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unburned fuel mixed with engine oil and
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a bad PCV valve can accelerate its
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formation when the valve fails to
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ventilate the crankase properly
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contaminants build up instead of being
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routed back into the combustion process
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over time this results in sludge
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formation particularly under the valve
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covers and around the oil cap sludge
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reduces engine lubrication clogs oil
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passages and increases wear on moving
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parts regular oil changes and a
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functioning PCV system are key to
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preventing this nine engine misfires a
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faulty PCV valve can disrupt the precise
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air fuel mixture your engine depends on
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and when that balance is off misfires
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are common a stuck open PCV valve allows
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excess air into the intake manifold
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which leads to lean air fuel mixture
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this can cause the engine to misfire on
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one or more cylinders which you may feel
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as a shutter or hear as a sputtering
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sound especially when idling or under
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light load misfires not only kill
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performance they also lead to poor fuel
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economy damage your catalytic converter
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and make your engine sound rough and
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unhealthy 10 failed emissions test the
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PCV system plays a major role in
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reducing harmful emissions by recycling
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crankcase gases back into the intake to
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be reburned when the valve fails the
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gases build up inside the crankase this
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buildup results in an imbalanced air
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fuel mixture increased hydrocarbon
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emissions and poor catalytic converter
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efficiency during an emissions test your
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car may fail due to high levels of
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unburned fuel or oil vapors in the
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exhaust in many regions a failed
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emissions test means you can't legally
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register or drive your vehicle until the
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problem is fixed now let's discuss the
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common trouble codes related to bad PCV
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0171 system 2 lean on bank 1
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P174 system 2 lean on bank
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2P300 random multiple cylinder misfire
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if your engine control unit triggers any
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of these trouble codes you should have
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been inspected your PCV valve by a
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professional now let's discuss how to
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inspect your PCV valve first gently pull
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or unscrew the PCV valve from its
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housing now hold the valve and shake it
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if you hear rattling sound from your
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valve it means your valve is in good
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shape next perform vacuum test apply
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vacuum to the PCV valve inlet the valve
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should open under vacuum and close when
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vacuum is removed if it doesn't move or
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leaks vacuum it's faulty if the valve
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passes all tests reinstall it if it
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fails any step you should replace it
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most OE&M PCV valves cost between $10 to
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$50 it is recommended to replace your
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PCV valve every 30,000 to 60,000 mi
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that's all for this video now that you
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know what to look for and how to
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maintain it you're way ahead of most
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drivers out there don't wait until your
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engine's begging for help check that
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valve and keep your ride running
