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The Care and Feeding of a Mass Air Flow Sensor

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Old 11-05-2008, 05:04 PM   #1
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Default The Care and Feeding of a Mass Air Flow Sensor

Ford uses a Hot Wire MAF System

Hot wire sensor (MAF) Theory of operation.

A hot wire mass airflow sensor determines the mass of air flowing into the engine’s air intake system. This is achieved by heating a wire with an electric current that is suspended in the engine’s air stream, not unlike a toaster wire. The wire's electrical resistance increases as the wire’s temperature increases, which limits electrical current flowing through the circuit. When air flows past the wire, the wire cools, decreasing its resistance, which in turn allows more current to flow through the circuit. As more current flows, the wire’s temperature increases until the resistance reaches equilibrium again. The amount of current required to maintain the wire’s temperature is directly proportional to the mass of air flowing past the wire. The integrated electronic circuit converts the measurement of current into a voltage signal which is sent to the ECU.
If air density increases due to pressure increase or temperature drop, but the air volume remains constant, the denser air will remove more heat from the wire indicating a higher mass airflow. Unlike the vane meter's paddle sensing element, the hot wire responds directly to air density. This sensor's capabilities are well suited to support the gasoline combustion process which fundamentally responds to air mass, not air volume.

Some of the benefits of a hot-wire MAF compared to the older style vane meter are:
  • responds very quickly to changes in air flow
  • low airflow restriction
  • smaller overall package
  • less sensitive to mounting location and orientation
  • no moving parts improve its durability
  • less expensive
  • separate temperature and pressure sensors are not required (to determine air mass)
There are some drawbacks:
  • dirt and oil can contaminate the hot-wire deteriorating its accuracy
  • installation requires a smooth parallel air flow across the hot-wire
It is dirt and oil on the sensor wire that causes the problems. Any coating on the resistance wire insulates it from the air flow and as the thickness of goo coating the wire increases it reports increasingly inaccurate information to ECM. This coating can be all but invisable to the naked eye. Accurate sensor information is vital for the ECM to compute the duration of a injector impulse. Inaccurate MAF information causes loss of power, poor throttle responce, and decreased gas mileage.

A Clean MAF Sensor means a Happy Engine.

Cleaning a MAF Sensor is simple as long as a couple of rules are followed

Touch this wire with anything and you will make the manager of the local parts store very happy when you are forking over for a new one.

2 Only use non coating cleaners designed to clean MAF Sensors.
carburator cleaner, degreasing sprays, window cleaner are a huge and expensive no-no! if you use any such cleaner chances are you too will be down at the local parts store purhasing a new MAF sensor.

How to clean the thing.

On Ford trucks the MAF Sensor (MAS) is located in the intake from the air cleaner assembly. According to most auto-tech's you are supposed to clean the MAS each time you change the air filter. It is so simple to do
I see no reason why you couldn't do it several times a year.

The sensor can be cleaned form either the air cleaner side or the air induction trunk side, which ever is easier. If from the air cleaner side open the air box up as if you where replacing the air filter from the top section of the box you can lift this part up and see the MAS and you can hose it down from there. If you take the induction trunk off you can get to the MAS from that side. You don't have to use a great deal of the spray cleaner on wire sensor just a couple of hard hits with the spray and you are finished. Put things back togather and if your MAS as not been cleaned in many years, like the one in my truck apparently was, your truck will move like a jackrabbit on speed pills.

It would seem the MAF cleaner made by CRC. look below, is the one everyone carries and it worked well for me.
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Last edited by transmaster; 11-05-2008 at 05:30 PM.
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Old 12-20-2008, 10:17 PM   #2
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Great info, I will also suggest that if you run a K&N or drive in very dusty, dirty enviroments that you remove the MAF and use the CRC in conjunction with a Q-tip and very carefully clean the hotwires as sometimes the baked on crud and oil from a K&N will not come off with just a few sprays... when the Q-tip stays clean you have a clean MAF!
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Old 12-20-2008, 11:41 PM   #3
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Good post. I should have thought of that. I just cleaned my MAF about a month ago.
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Old 12-26-2008, 11:11 AM   #4
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does an 1988 have one of these?
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Old 12-28-2008, 03:26 PM   #5
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Originally Posted by swjb View Post
does an 1988 have one of these?
Nope, Not unless its been modded w/one. but that requires a computer & wiring harness transplant. Yours would be MAP. If your planning to keep your truck it's not a bad idea. An additional BIG benifit that comes w/ a MAF mod is sequentially fired injectors instead of split bank. I've got an 87' 302 w/ 77Kmiles and only 2psi variance in compression between cylinders. It's the second most trouble free and dependable of the 10 or 11 Fords I've owned so I'll be down harvesting for a MAF mod next Sunday at the local salvage yard. Oh, my favorite was my first vehicle & Ford. 63' E-100 straight six Falcon, manual w/ 3 onda tree and a box bolted to the floor that was a heater that could melt tennis shoes. Might have had a little to do w/ it being the first van conversion at my high school, but it was running strong when I sold it w/ 285k miles.
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Old 05-20-2009, 05:53 PM   #6
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Default Good Info:

Very informative article....even a Chevy owner can comprehend it.

FYI: I clean the MAF sensors using a good quality aerosol electronics cleaner (the CRC looks even better) and a camel's hair artists' brush....VERY GENTLY.

Last edited by Kattumaram; 05-20-2009 at 05:57 PM.
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Old 08-02-2009, 11:48 PM   #7
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so is it necessary to remove the sensor from the intake? the can says to, but the way i read that it sounds like you said i can just turn the intake tube holding it upwards and spray down in it onto the MAF sensor and call it good.
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Old 08-03-2009, 01:33 AM   #8
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when i put my CAi in my truck i forgot to connect the maf sensor. took off for the first ride and said F that im not gonna take this ugly ride just for some better airflow,etc.. open the hood to start takin the CAi off and saw i forgot it lmao. took it again and felt so much more smooth when letting off the pedal. check everything twice lol
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Old 01-16-2010, 03:31 PM   #9
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Will any quick drying electrical contact cleaner work?
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Old 02-01-2010, 01:09 PM   #10
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Thanks for the good info... I'll have to try that out. Maybe it'll put a spring back in her step.
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