Cleaning the MAF
Q. But how can it get dirty? Surely there is an air filter to keep it clean?
A. Well, yes there is, but air has to be allowed through, and with it microscopic pollen and other organic material which burns when it comes into contact with the sensor wire, which is maintained at 200 degrees C. The MAF electronics measures the amount of current required to keep the wire at this temperature, against the cooling effect of the inlet air flowing past it. Hence the current required is a measure of the actual airflow.
Disclaimer – this information is taken from various different tech sites, including;
http://www.motorage.com/http://www.aircarecolorado.com/http://www.fordscorpio.co.uk/cleanmaf.htmetc. (quick search on google)
some of it has been modified to suit the swift
you can potentially damage your sensor, attempt this ‘fix’ at your own risk.The Hitachi style MAF sensor (figure1) is used on the Swift GT/GTi engines. It is a hot wire type sensor, which uses a platinum wire with a glass-ceramic coating over its center section. It does not use a burn-off cycle on vehicle shut down, which may be why it has problems with contamination. As the MAF inevitably becomes coated in soot the readings for the ecu become less and less accurate, but the ecu has no way of knowing this. It must accept the reading, and since the ecu uses the MAF to determine airflow for fueling, idle (with the IACV), etc. performance & fuel ratios are skewed.
figure1
The Sensor consists of a screen to break up air turbulence, a thermistor to measure the temperature of the incoming air, a heated element and electronic module (figure2). A small passage inside the sensor directs part of the airflow past the thermistor and the heated element. The module measures the electrical current required to maintain the heated element at a constant temperature.
figure2
The output signal is analog (0-5V) which is then converted by the PCM into a mass airflow rate measured in grams per second.
Diagnosing Contaminated Mass Airflow Sensors
MAF sensors can get contaminated from a variety of sources - dirt, oil, silicone, spider webs, potting compound from the sensor element itself, etc. When a MAF sensor gets contaminated, it skews the transfer function such that the MAF overestimates airflow at idle (causes the fuel system to go rich) and underestimates airflow at high airflow (causes the fuel system to go lean). This means that Long Term Fuel Trim will learn lean (negative) corrections at idle and rich (positive) corrections at higher airflow. If a vehicle is driven at WOT (Wide-Open Throttle) or high loads, the fuel system normally goes open loop with a rich mixture to provide maximum power.
Repairing/Cleaning
keep in mind that this is a very delicate sensor Alt.1the internal wires of the sensor. One is the hot wire and the other a precision resistor. You can see how fragile they are - don't drop the sensor onto a concrete floor, or prod about in there with anything - if the wires break the MAF is junk and they are quite expensive to replace so TAKE CARE.
After a couple of squirts of carb cleaner, which very quickly evaporates, the sensor wires were bright and shiny again. I replaced the rubber O ring with a smear of light oil and then bolted up the MAF sensor to the air filter box. I then lubricated the rubber hose with another smear of oil and pushed the other end of the MAF sensor into the inlet pipe and re tightened the hose clip. Reconnecting the multiplug finished the job.
Result? Smoother running on tickover, and smoother throttle response.
NOTE: take care that the sensor hoses are properly sealed against leaks.
Alt.2 Ok, so out with the "carb and injector cleaner" spray can, I fasten a little tube on the end of the nozzle, test it, and then spritz away liberally. Cleaner drips out of the other end of the sensor cross member, but the wires are miraculously undamaged.
But not quite clean, now that the wires and chamber are mostly shiny silver, a few dregs of dark matter remain, so some more fizzing with the spray can until they are completely clean. Then a couple of squirts down the tube into the engine, clean up the MAF fittings and a drop of light oil to ensure a tight seal around the rubber ring and the whole thing goes back together the way it was to begin with.
Also, don't forget to connect the electrics, this is probably the one that will be forgotten if anything is. your car will not make it out for the driveway, but it will still start.
Alt.3Removing the MAF sensor on the Swift is easy. Just remove two screws and the wiring connector and the sensor module is in your hand. A close visual inspection may show there is a fuzzy build-up on the sensing element. This requires a bit of scrubbing with a soft toothbrush (
warning, this was what was recommended in only 1 article, scrub at your own risk!!! ) and some throttle body cleaner. Just spraying the sensor wire may not remove the fuzzy build-up (small fibers from the air filter). follow this with some brake cleaner and compressed air to make sure there is no residue on the sensor that would attract more dirt. (
warning, again, sounds pretty extreme ) Re-install the sensor module and see how it works.
(please post any personal success/failure here, thanks)
Login
Register
Gallery
FAQ
Search
