Do any of you guys use k&n or similar "oiled" aftermarket air filters? if so you have to be extremely careful when cleaning and reoiling them not to get too much oil on the filter and let it dry complete before reinstalling. the oil for the filter will ruin a MAF sensor due to coating the wires with oil and then when the MAF heats the wire it burns it in to it and bam sensors bad. The instructions from k&n on re oiling say let it wick for 20+ minutes I go much much longer then this 3 hours minimum and usually try to do the cleaning in the evening or right before bed(when I know I wont have to use the car that night again) and re oil and let it sit on a few layers thick of paper towels over night to ensure its dry 100% in the morning then reinstall. MAF cleaner is a worthwhile thing to do but will not solve a faulty sensor. I also use maf cleaner and clean the intake and filter box as well as the MAF sensor at this same time.
if you don't use performance type filters like this but use stock paper ones make sure they are changed every 10-15k miles or at least annually if you drive less then this amount a year (even if the manual says longer, trust me most places especially in cities with road work get so much dust and crap sucked in that they get over full before 24-30k interval in the manual) this prevents the filter from becoming clogged and letting tiny dust particles by as it cannot hold anymore and has to release some its holding to hold new ones (the air is forcing them out) these particles then flow into the intake and hit the MAF sensor, well a maf sensor works by heating a razor thin wire really hot and then senses air density and temp by how much the air coming by cools this wire off, the wire gets extremely hot, its almost like a halogen light filament, well this melts these particles onto the wire and after too much builds up cleaner wont get them off and the sensor cannot sense any difference in air as it heats the wire so then it throws the CEL on and pus the car into a predefined fuel map and you get worse performance and mpg or even hard or no starts because the MAF sensor is the main sensor the computer talks to. they communicate air volume,density and temp by 1s and 0s changing constantly same with 02 sensors in the exhaust, in fact o2 sensors and maf senors work very similarly. the only way to be sure your maf sensor is bad is to change it, if you don't have a medium-high dollar scan tool that can do live data and see the maf readings, but you would also need the specs for normal operation under the test conditions to determine anything with this. or a voltmeter that can read 10,000+ ohms and have the specs for resistance under test conditions for a normal working sensor so you can determine if it is out of spec and bad
