I have a 2002 Kia Sportage and have decided to replace my own master airflow sensor. I am not doing this out of any expertise or desire except I can’t afford to have the mechanic do it and it needs to be done as I already had them replace the oxygen sensor and that did not do the trick. I am trying to find the schematic on the internet rather than buy the Chilton Manual, again out of penny pinching. Is there anywhere on the internet to find such info? I have not been successful with that and had been told it was easy enough to find. Any thoughts, suggestions would be great.
Try autozone.com, set up an account (it’s free), they might have that info. Also, it’s a ‘mass airflow sensor’.
Before you go blowing $$ on a mass airflow sensor, why don’t you report the actual problem you are having. Of all of the strategies for fixing cars, guessing is often the most expensive.
I’m going to assume that your check engine light came on and that you have an error code. The error code format is “P1234” - post your code(s). Also post symptoms, if any, basics about the state of the car’s maintenance and what, if anything has actually been done to find the source of your problem.
Mass airflow sensors can be cleaned.
Also, if you don’t know what the codes are, you can borrow a code reader at a local chain parts store like Autozone or Advance Auto Parts. Call ahead to see if they have one and it is in working condition. They won’t charge you anything to borrow the code reader.
This may help: http://cardone.com/english/club/Products/ELECTRONICS/Protech/Tech_Bulletins/PT%2074-0002.pdf
I did go to Autozone who sold me my as they called it, Master Air Flow Sensor. How would I know if the sensor could be cleaned as opposed to replaced. the car has 163,000 miles.
By removing it, cleaning and re-installing it. Then clear the code and see if it comes back. If you don;t have a code reader you can clear the code by disconnecting the battery for a minute or so.
I have read dire warnings about terrible consequences from disconnecting the battery but I have never experienced any.
“master”? sorry, it’s “mass”. Tells you a little about some folks are car parts places. How much does it cost? Have you bought it yet?
What is the error code? Oh, and did I forget to ask what the error code is?
If you want to clean it Autozone (and any other parts store) has a can sitting on the shelf with other cleaners called “MAF Sensor cleaner.”
As long as 1) You didn’t have to special order it, and 2) you haven’t used it yet, you can return it.
I would (if you aren’t sure exactly what the sensor is):
1) hang onto the new (as yet unused) mass airflow sensor…only for a few hours…
2) get the cleaner
3) use the new unit to make sure you’re looking at the right part
4) remove and clean the old one, and reinstall it
5) return to the store, ask them to check and clear any codes
6) return the new, unused unit
If you do know what/where it is, skip 1 and 3. 
Good luck,
Chase
I’ve attached a little description of what a Mass Airflow Sensor is.
I believe your car uses a hot wire type. The wire does deteriorate over time from being heated, and the resistance changes, and with 163,000 miles I would not be surprized if yours has. It’ll be located in the air intake, just behind the air filter. Your best bet is to look the location up in a Haynes repair manual. Since you have the new one in-hand already, you can use that as a reference.