THE AIR FLOW
METER
Identify, Troubleshoot and Cure Air Flow Meter problems
What is an air flow meter(AFM);
how would you recognize it and what does it do?
The Air Flow Meter
(AFM) is an important component in regulating fuel delivery to the engine.
All modern petrol and diesel engines(about 1993 on) have an Air Flow Meter.
How can I tell if my
Air Flow Meter
is faulty?
|
engine idles
erratically
hesitates when you accelerate
check diagnostic fault code |
What are faulty
Air Flow Meter
symptoms?
|
poor performance, rough idle,
hesitating, lack of power |
Things to check
|
Dirt and/or water getting into air intake..
check and replace filter
Electrical connector corroded, wires broken
Splits/leaks in air intake tubing..
Other sensor and regulators
e.g. EGR valve, pressure sensor
|
What effects will failure have on the
performance of your car?
The eiest indication is, of course the malfuntion light
showing on your dhboard!
Generally the car will start but will run erratically and may even cut out, using more fuel and performing
poorly.
Engines with carburettors do not
need an AFM because the carb itself regulates the amount of fuel and air going into the engine.
How to find the air flow meter on you car
Look for the air
intake opening, follow it to the air filter and usually you will find the AFM either in the filter box or clipped
into the pipework going to the engine
What does the AFM look like?
Photo shows a typical pltic cylinder type of AFM....
......which h been dismantled from its pipework.
Most AFM have an electrical connexion into them. Check this plug is not corroded inside
What does
the AFM actually do?
The AFM tells the Engine Control Unit (ECU) how much air is flowing
into the engine;
this allows the ECU to control the amount of fuel delivered to the injectors.
Plee click here to view air flow meter in stock
What are the different types of MAF used in modern cars and how do they
work?
The earlier type of AFM (eg Bosch Jetronic) used a vane or flap inside the meter body; air
psed by it opened the flap.
A spring then returned the flap towards closed position when the engine speed slowed down.
Later types are called hot wire; air flow (over the wires) is meured by how much
current is required to keep the wires at a predetermined temperature.
Look inside and you can usually see two filaments; these have to be thin to meure accurately the
speed at which air is flowing into the engine.
Which companies make air flow meters? Are there
pattern copies on the market?
Original equipment fitted to European cars is made by companies like Bosch, Siemens and Hella and,
yes there are a lot of pattern copies on the market. Depending on budget you may prefer to fit a
genuine replacement.
How ey is it to change the air flow meter
yourself?
Fortunately it's an ey job, requiring no special skills or
tools.
© by Andy Hewing B.Sc.
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