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hey folks Scotty Bryan here and let me
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tell you I've seen a lot of cars in my
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day today we're talking about a problem
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that's plagued car owners since the dawn
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of the dang combustion engine your car's
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RPM fluctuating at idle you know what
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I'm talking about you're sitting at a
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red light minding your own business and
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suddenly the engine's doing the chaa
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well don't worry because in this video
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I'm going to give you the straightup non
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nonsense reasons why this is happening
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we're going to go through seven shocking
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reasons and let me tell you mechanics
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hate reason number three so buckle up
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grab a wrench and let's get this thing
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figured out first up we got vacuum leaks
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now your engine needs a delicate balance
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of air and fuel to run smoothly like a
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well-oiled banjo but when there's a leak
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in the vacuum system it's like poking
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holes in your banjo throws the whole
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thing out of whack that leak lets in
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extra air the engine wasn't expecting
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messing up the air fuel mixture and
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guess what that throws your RPMs into a
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tizzy you might notice rough idling poor
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acceleration even engine stalling now
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finding a vacuum leak can be trickier
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than a greased pig at a county fair but
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we'll get to that later next up we got a
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dirty air filter this one's a classic
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folks and it's about as common as a
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mosquito at a picnic see your engine
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needs to breathe just like you and me it
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sucks in air to mix with the fuel and
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the air filter's job is to keep out all
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the dirt and Gunk that can clog things
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up but when that air filter gets clogged
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it's like trying to breathe through a
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straw the engine has to work harder to
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get enough air and that can make your
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RPMs bounce around like a jumping bean
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plus a dirty air a filter can even hurt
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your fuel economy nobody wants that now
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this next one this is the one mechanics
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hate the dreaded idle air control valve
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or IAC valve for short this little guy
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is responsible for controlling the
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amount of air that bypasses the throttle
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plate when the engine's idling think of
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it like the fine-tuning knob on your
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engine's idle speed but when the IAC
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valve gets gunked up or just plane wears
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out it can't do its job properly that
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means your idle speed can fluctuate
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stall or even rev up unexpectedly and
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let me tell you diagnosing a bad IAC
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valve can be a real pain in the neck
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it's often overlooked and mechanics will
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throw Parts at it all day long trying to
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fix it chapter 4 next up we got bad
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spark plugs now these little guys are
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responsible for igniting the air fuel
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mixture in your engine cylinders they're
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like the sparklers that set off the
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fireworks but when your spark plugs are
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worn out they can misfire that means the
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fuel isn't burning properly and that can
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cause all sorts of problems including
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rough idling and fluctuating RPMs now
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spark plugs are relatively cheap and
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easy to replace so it's always a good
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idea to keep them fresh chapter 5 fuel
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system issues starving your engine now
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let's talk about fuel system problems
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just like your body needs food your
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engine needs fuel to run but if there's
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a problem with the fuel system your
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engine might not be getting the fuel it
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needs and that can lead to all sorts of
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issues including fluctuating RPMs one
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common culprit is a dirty fuel injector
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over time Gunk and varnish can build up
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on the injectors clogging them up and
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preventing them from delivering the
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right amount of fuel another possibility
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is a failing fuel pump if the fuel pump
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is weak or dying it might not be able to
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supply enough fuel to the engine
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especially at idle chapter 6 throttle
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body problems the air gatekeeper
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malfunctions now the throttle body is
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like the gatekeeper of your engine's air
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intake system it controls the amount of
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air that flows into the engine but just
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like any other part the throttle body
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can get dirty or malfunction when the
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throttle body gets gunked up it can
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disrupt the smooth flow of air into the
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engine causing rough idling and
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fluctuating RPMs in some cases the
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throttle position sensor which tells the
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engine how far open the throttle plate
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is can also fail sending incorrect
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signals to the engine control unit and
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messing up the idle speed chapter 7
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electrical Gremlins when the current
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goes haywire and finally we come to
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electrical problems now these can be
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some of the trickiest problems to
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diagnosed because they can be
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intermittent and hard to pin down one
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common electrical issue that can cause
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RPM fluctuations is a failing alternator
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the alternator is responsible for
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charging the battery and powering the
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electrical system while the engine is
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running If the alternator is weak or
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failing it can cause the electrical
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system to become unstable leading to all
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sorts of strange Behavior including
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fluctuating RPMs other electrical
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Gremlins that can cause this issue
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include a failing battery a bad ground
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connection or even a faulty sensor keep
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your engine happy and your RPM steady so
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there you have it folks seven shocking
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reasons why your car's RPM might be
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fluctuating at idle remember a smooth
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idle is a sign of a Happy Engine and
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nobody wants a grumpy engine on their
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hands if you're experiencing this
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problem don't ignore it get it checked
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out by a trusted mechanic preferably one
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who doesn't throw a fit when they see an
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IAC valve and remember regular
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maintenance is key to preventing these
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problems in the first place so keep your
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engine happy keep those RPMs steady and
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I'll see you in the next video if you
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found this video helpful don't forget to
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like subscribe and hit that Bell icon
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for more car tips and tricks thanks for
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watching and I'll see you next time
