I wasnt able to find any info on the toyota forums regarding modifying the MAF so I just went by memory from my last 4runner and went ahead and did it.

So the theory is... if you tighten the spring it takes more air-flow for it to open it up giving you better fuel economy. If you losen the spring it will give you more fuel and less economy. Before you start, mark the starting point and turn in increments of 3 and test it. You can use a A/F guage to get things a little more percise.

Start by cutting around the top with a sharp razor blade

Lift the lid off with the blade carfully. Be sure to clean up all the old silicone on the maf and the lid

Couple inside shots



On the far left side if a black metal hangar that holds the dial into place. You need to use a screwdriver and press this "lever" back and turn the dial in whichever direction you are trying to go. Release the lever and you're set. I am pointing at the lever in the picture


PLEASE DO NOT FORGET TO SILICONE THE TOP BACK TOGETHER.

 

What year is this mofication on?
How does the turning of the MAF change performance?

 

this was done on a 1992 3.0 ..... but any maf with a"flap style" design this should apply to. How i works: the more airflow your engine gets the wider the flap opens richening the fuel mixture. I chose to tighten my spring so the flap does not open as far leaning out my fuel mixture. If you want to richen your fuel, losen the spring so the flap opens prematurly

 

I would suggest doing some research on the effects of leaning out your engine and running it rich before doing this mod.
This comment is not directed at the anyone in particular, just think that anyone considering should do some reading on potential side effects before diving into it.

 

ill pull my plugs in a week and take pics

 

I highly suggest getting a wideband before doing this, too lean = blown motor, too rich = flooded motor. I mean those are worst case scenarios but still, too risky IMO.

BUT

To each their own.

 

Think of it this way. You've got 400,000km on your angine... after all this time the spring is starting to get weak and starting to make your engine run really... think of it as "RE"-tightening the spring

I still agree this needs to be looked into a little more, but everyone seems to whine about fuel economy and this seems like a quick simple bandaid.If someone has a spare MAF and a a/f guage mabye you could help out

 

Technically it's a AFM....just sayin....little different...I'm sure SOMEONE on here is just ITCHING to throw up an FSM schematic....

 

I'd be interested in seeing the results through the eyes of a wide-band...

 

The dial is spring tension for the gate. The way I see it.
If,say you have a snorkel, the air flow is restricted and only then would I change the spring setting to looser. So the gate opens easiser.but then you still have to keep it within range and still have the fuel shut off work.
So you mark the black arm position and loosen the Allen head bolt. And make tiny adjustments till your Meter now works within the service specs. Other than that I wouldn't mess with it. Just turnning the plate only throws the whole system off. Now I DON'T recommend doing it unless you have a spare, or at all for that matter.
But I have done it on trucks I owned it the past and it solved so many issues I had in the past. A dyno and old school analyzer was used to nail it.
It was not a easy task what so ever. I had to make sure every thing else was working properly and no other ecu issues first.
Mostly a last resort when everything was replaced on the truck and it ran like crap. I just did the same thing the factory did and set it as if it was new. No problems with those trucks after that. But that's me.

 

The VAF sensor measures the air flow into the engine with a spring-loaded air flap/door attached to a variable resistor (potentiometer). The vane moves in proportion to the airflow, and a voltage is generated in proportion to the distance the vane moves, or the movement of the vane directly regulates the amount of fuel injected, as in the K-Jetronic system.

Many VAF sensors have an air-fuel adjustment screw, which opens or closes a small air passage on the side of the VAF sensor. This screw controls the air-fuel mixture by letting a metered amount of air flow past the air flap, thereby, leaning or richening the mixture. By turning the screw clockwise the mixture is enriched and counterclockwise the mixture is leaned.

The vane moves because of the drag force of the air flow against it; it does not measure volume or mass directly. The drag force depends on air density (air density in turn depends on air temperature), air velocity and the shape of the vane, see drag equation. Some VAF sensors include an additional intake air temperature sensor (IAT sensor) to allow the engines ECU to calculate the airs density, and the fuel delivery accordingly.

The vane meter approach has some drawbacks:

The car's ECU compensates by opening the throttle wider to admit more air. This, in turn, decreases the resistance the engine must overcome to suck air in. The net effect is for the engine to intake the same amount of oxygen (and thus burn the same amount of fuel, producing the same power) but with less friction losses, allowing for a gain in fuel economy, at the expense of top-end power.
Doing this mod is risky because of the afore mentioned 'detonation' from a lean fuel mixture. Mod your vafm if you want, just be fully aware it may bite you in the end.