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the old antrx.com wiki => old wiki articles to be converted => maintenance issues => Topic started by: noss on Dec 29, 2004, 02:23PM
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looking after your air flow meter
[author] noss
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also know as a 'mass air flow sensor' (MAF sensor) the air flow meter (AFM) found in your engine bay is a delicate piece of electrical equipment vital to the running of your engine. nissan afm's are a hot wire type, meaning that they sense the air flow being drawn into your engine literaly with a hot wire filament.
the way this works is that the wire filament is set to maintain a certain temperature. at idle, there isnt much air entering the engine and as such, the wire filament requires less voltage to maintain its set temperature. as more air enters the engine, the wire is cooled by the passing air, when this happens, the sensor will regulate the filament's temperature by increasing the voltage passing through it. this voltage figure is then passed back to the ecu to help calculate your engine's air fuel ratios, the maximum voltage that your ecu will accept is 5.0v, when the voltage returned to the ecu reaches 5.1v this means your afm has been maxed out and the ammount of air flowing into you're engine exceeds the resolution of your afm. different afm's have different maximum flow readings, but this is something for different tech article.
as you can imagine, it is very important that your air flow meter is in perfect operating condition to maintain maximum fuel efficiency and to obtain maximum power from your engine, if the delicate filament in the sensor is fouled your engine may not be running at its optimum.
the main cause of the afm filament fouling is caused by oiled air filters such as pod filters and k&n panel filters. when oiled from the factory they generally cause no problems, the problem only occurs when the user cleans and re-oils the filter themselves and they over-oil their filter, this results in the engine sucking the oil from the filter at high rpms and in turn some of the oil will coat the hot wire filament, this will cause the 'ECM' light to flash at times, often randomly. its usually difficult to troubleshoot at first because no error codes will be stored in your ECU.
cleaning the filament is an easy task, all that you require is some simple tools to remove your air flow meter (tools required would depend on your intake setup or what kind of air flow meter you have) and some crc brand contact cleaner which is available at any dick smith, jaycar or similar store.
to clean the filament, remove your afm/sensor from your engine bay, spray on the cleaner and let the sensor sit for 15 or so minutes. spray it again for good measure. some people recommend using a toothbrush to lightly scrub the filament but you must be extremely careful as you could easily break it. my personaly preference is to just spray the filament 2-3 times.
once the filament has had a good dose of the electrical contact cleaner and has had sufficient time to dry, re-install the afm/sensor.
the next step is to clean your air filter. give it a good tap on a hard surface to dislodge the larger debris. the next step is to flush it with water IN THE OPPOSITE DIRECTION THAT THE AIR NORMALLY FLOWS. this prevents dust an other particles being further driven into the filter medium. let your air filter dry out, DO NOT DRY IT IN THE SUN OR WITH A HEATING DEVICE, if your air filter was excessively oiled you will most likely not need to oil it again before installation. if you do feel that your filter needs to be re-oiled, follow the directions that came with your filter cleaner kit and oil it sparingly. once you're satisfied re-install your air filter.
when you start your car you shouldnt have the 'ECM' light flashing again, at least that is until you over-oil your air filter.
pictures to come.