Air Flow Meter Troubleshooting?

I suspect my air flow meter is bad. The ohms readings, as per the factory manual, are not bad, but the progression of the values (all between 150 and 800, approx), as the valve opens, are not linear. Is this a bad thing? TIA

I do not know about the toyota truck but if the mas airflow meter's wires that change with resistance are dirty, it will affect the voltage values sent to the ecu. plast the wires with some carb cleaner and run the engine again it may improve its fuel and or performance number. check the filter to.

Sorry this post is so late, but I just noticed!

I recently changed my VAFM because I thought it was bad due to the same resistance tests that you reported. The manual and other sources say the resistance will change in a "wave" pattern, which is not the same as a smooth, linear move. I ended up changing the VAFM and the new one tested exactly the same. I installed it anyway.

No change until I replaced the egr vacuum modulator, which bumped my mileage up over 25%!

I still have a good toyota VAFM (#22250-65030) if you think you still need it.

Is that the airflow meter with a movable door that moves in accordance with airflow? or is it a wire like on some other system that changes resistance with the proportional airflow moving across it?

How would you have tested this unit? I imagine in the factory book or mitchel manual there is a process on how to test this and the egr modulator.

If your egr was stuck open it would cause a lean mixture to the engine at idle and would contribute to rough running idle issues, stalling and higher then expected cylinder temperatures.

Do you know if there is a online manual to test these systems? I hope I dont come across this without a manual or I will be stuck explaining to a customer why the part did not fix the problem.

Yes, a "Vane Air Flow Meter", or VAFM is the one with the door that gets pushed open by the air after the filter.

The test for the moving vane part of the VAFM is not straightforward, because it isn't easily measurable. Like I said, it's not a smooth linear sweep when you measure the ohms, but an up and down wave measurement. That's why I thought it was bad.

There is a test for the EGR vacuum modulator. unplug the three top tubes labeled Q, P & R. Plug P & R with your finger and blow into Q. Air should flow freely. Start your engine and rev to 3500, plug P & R and when you blow into Q, the air flow should be low to none. Others have said if you can blow through the bottom port (the exhaust port), you should not be able to or there is a big leak.

In my case, trying the first test, air did not flow as freely as I thought it should through port Q, so I replaced it. It gets old and doesn't work so great after 15+ years.

I have a factory manual, but I have seen the test pages posted for both the VAFM tests and the EGR vacuum modulator tests. You should be able to find them.

Try using the toyota tech search search engine:
http://www.wattora.com/index.php?page_id=72