testing MAF sensor? - Toyota Nation Forum : Toyota Car and Truck Forums

toysports2k · 05-06-2005, 06:15 PM

What's the story on testing the 22RE mass air flow sensor? Howz that done?

burger · 05-08-2005, 05:31 PM

What do you want to test?To make your fuel pump run,the flap inside the maf must move open a little.Turn your key on and push the flap,you should be able to hear the pump run.

OEMonkey · 05-09-2005, 12:28 AM

its not a maf sensor, its an afm.

its input is not needed to turn on the fuel pump, but is one of the inputs used to determine injector pulse width.
theres a resistance check you could do bet. each terminal after you disconnect the connector. measure bet. vs and e2(this checks the flapper). at fully closed position you should get 200-400 ohms, and resistance should increase when you open the flapper. you can do a v drop test on the same pins when its connected but you'll have to backprobe w/ the koeo. to check resistance on the IAT(integral to the afm), measure bet e2 and tha. you'll need a repair manual for exact resistance specifications and terminal pin locations.

texas12 · 05-09-2005, 06:29 AM

Call it a MAF or AFM but on my 4runner, the flapper must move off closed for the fuel pump to turn ON (just like burger said).

OEMonkey · 05-09-2005, 12:18 PM

interesting. so every time you start your vehicle, someone has to manually open the flapper on the afm while you turn the ignition key otherwise it wont start bec. there will be no fuel pressure, correct? I've started many afm based efi engines by just turning the ignition key and closing the clutch start switch(m/t) w/ my left foot.

you can energize the fuel pump(assuming its in good working condition) even w/ the afm connector disconnected by jumping b+ and fp on the dlc.

Toy Sport 4x4 · 05-09-2005, 03:19 PM

That is true about the terminal jump. These types of engines are supposed to keep fuel pressure built in the lines that way when you start cranking it will start. The engine will create vaccum to open the flapper though so it will crank. Sometimes when it takes a long time to crank the engine it is because the pressure has bled off and the engine has to suck the flapper open to get fuel back to the cylinders

texas12 · 05-09-2005, 06:03 PM

Quote:

Originally Posted by OEMonkey

interesting. so every time you start your vehicle, someone has to manually open the flapper on the afm while you turn the ignition key otherwise it wont start bec. there will be no fuel pressure, correct? I've started many afm based efi engines by just turning the ignition key and closing the clutch start switch(m/t) w/ my left foot.

you can energize the fuel pump(assuming its in good working condition) even w/ the afm connector disconnected by jumping b+ and fp on the dlc.

Yes, that is correct! There is a little person called the Engine Compression Man that opens the flapper on the afm to activate your fuel pump. Without compression, the flapper does not open and the fuel pump does not come on.
There is a jumper to activate the fuel pump but if you do not know where it is, then manually opening your flapper is the next best thing.

Toysrme · 05-09-2005, 06:05 PM

3vz-fe AFM. It's very different in signal outputs, but you get the idea.

burger · 05-09-2005, 08:14 PM

I've got an alfa romeo with bosch fuel injection and they call it an"air flow meter"-AFM- and I believe Toyota calls it"mass air flow" -MAF- 6 of 1,half dozen of the other,any way,there's a site dedicated to alfas that examines tuning these suckers if you want .italian cars section at www.oldebottles .com

toysports2k · 05-11-2005, 01:23 PM

Thanks to all who chimed in on this one for me! I've ordered a new post-cat O2 sensor that i should be receiving today. After installing that, I'll check the resistance and volt drop on the MAF/AFM (whatever you wanna call it) to see if that's where my over-rich problem might be originating from.