A modern engine really needs to know exactly how much air is drawn into the engine, how dense it is,
and what temperature it is to allow for efficient combustion.
Clogged Air Filter
A clogged air filter means the
engine can’t get enough air, which causes it to
reduce the amount of fuel delivered and can result
in the engine losing power. Check your filter on a
regular basis.
Dirty MAF Sensor
The MAF contains a small wire
that heats up to measure the density of the air
going into the engine. If the wire gets dirty, it will
not read properly. The MAF can be cleaned, but you
need to buy a special cleaner from the auto parts
store that’s made specifically for cleaning the
sensor.
Faulty Throttle Position Sensor
The throttle body
is a mechanical plate, so it usually doesn’t have
problems, but the sensor that tells the computer to open it can fail. The TPS may have to be
calibrated and aligned; if so, leave this replacement
to a professional.
Faulty EGR System
The EGR valve can become
clogged and fail. The engine may run rough, stall, or
not run at all.
Clogged or Sticking PCV Valve
Like the EGR, the
PCV valve can become clogged or stuck. If this
happens, the engine will start to lose power or
not accelerate, or the pressure can build up in the
crankcase and cause seals to fail. Checking the
PCV is easy and quick, and in most cases
relatively inexpensive to replace.
Clogged or Failed IAC
The IAC allows a small
amount of air to bypass the throttle plate at idle.
If the valve fails or clogs, the engine may come off
acceleration slowly, or it may stall and come down
too fast. If it is closed, the car may not start and
run at idle.
LOW OR NO FUEL PRESSURE
When the engine starts losing fuel pressure, the injectors can’t deliver enough fuel to allow the engine to
run smoothly. Many times the engine will start vibrating if it starts to lose power.
Loss of fuel pressure can happen at any point in the fuel system—the screen inside the fuel tank can be
clogged, the fuel pump itself can fail, the fuel filter can be clogged, the lines can be blocked, or the fuel injectors
can be dirty.
Clogged Fuel Filter
If your car has a replaceable
filter, it can be checked and replaced relatively
inexpensively. Some newer cars do not have a
replaceable fuel filter, as it is part of the fuel pump
assembly mounted within the gas tank of the car.
Faulty Fuel Pump
Some fuel pumps use plastic gears,
and running the incorrect fuel can destroy the pump
by dissolving the plastic parts. This can happen
when you try to run alcohol-based fuels in a car not
designed for them.
The fuel pump may also stop running because it
wears out, or the electricity running the pump
may fail. There are usually a fuse and a relay
powering the fuel pump, and these go bad more
often than the pump does.
Clogged Fuel Injector
The fuel injector has a little
needle opening that moves back and forth. Small
particles of dirt occasionally get past the filter and
may build up on the injector, or poor fuel can gum
it up and prevent it from working. Contaminants
can also partially block the opening and prevent
the fuel from spraying out properly (atomizing),
resulting in the fuel not mixing with the air as it
should.
One preventative maintenance step you can take is
to run a bottle of fuel injection cleaner through
your engine every time you have the oil changed.
However, if you have a clogged injector, you will
have to use a professional-grade cleaner or have it
cleaned by a professional.
Open Gas Cap
One of the most common computer codes comes from leaving the gas cap off
of the gas port, which means the vapors from the
tank are not being drawn into the engine through
the EVAP system.
Inertia Fuel Switch
Some car makers use a switch
to shut off power in a wreck. If your car gets
jostled, the switch can trip and close. If the car
won’t start, try resetting the switch. Some car
makers use oil pressure or other means to shut off
the fuel.
Clogs and Leaks
Inspect your fuel lines for leaks
on a regular basis. Fuel lines are made out of solid
and flexible materials, and both can fail. Flexible
lines wear out and hard lines can be kinked or
rusted.
Sensors
Since your car relies on sensors to know
how much fuel is being delivered, the car won’t
run properly if a sensor goes bad. When a sensor
goes bad, the computer may send an error code
that the sensor is out of range.
