Minute Mod:
Adjusting the Air Flow Meter
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| Http://www.4x4wire.com/toyota/minutemod/afm/ |
Short Cuts |
| Author: Harry Wagner May 2002 |
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| The air flow meter out of the vehicle. |
22RE motors are famous for their reliability, not their power. Common modifications such as free flow air filters, camshafts, and exhaust headers can help give Toyota trucks more power to turn big, heavy tires. These modifications increase air flow and can cause a lean condition. Too lean of a fuel mixture can result in detonation and holes burnt in pistons in extreme cases. 22RE motors utilize a air fuel meter (AFM) system, as opposed to mass air flow or speed density, in order to regulate the air entering the motor. The AFM is essentially a flapper door attached to a flat wound spring. As air passes the door the spring moves. This movement is then translated into an electric signal that tells the electronic control unit (ECU) how much fuel to deliver. A modified engine will move more air through the engine on a given combustion cycle than a factory motor, so the AFM must be adjusted to compensate. This is an easy modification that only requires a razor blade and a Phillips screwdriver.
- Start by locating the AFM, which is directly behind the air box.
- Next use the razor blade to cut through the silicon around the black plastic lid on the AFM. Once the lid is open you will see the flat wound spring previously referred to.
- Make sure to mark the location of the gear relative to the spring before making any changes. We used a felt tip pen to make our mark.
- Next loosen the screw that is connected to the clip that holds the gear in place. It should be possible to move the gear without completely removing the retaining clip.
- Turn the gear counter clockwise to loosen the spring and richen the fuel mixture. We suggest only adjusting the gear one tooth at a time until the correct mixture is achieved. Too rich of a mixture will result in poor fuel mileage, sluggishness at lower RPMs, and excessive exhaust emissions.
- Tighten the screw and close the lid on the top of the AFM. Once the mixture is dialed in, it is advisable to reseal the lid of the AFM with silicon. The internal components are quite fragile and susceptible to water damage.
- Pull the 15 amp fuse under the dash for the electronic fuel injection (EFI) for several minutes in order to reset the ECU.
- It is now time to go test the modifications for any improvement in the fuel mixture.
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| The internals of the AFM. |
Marking the initial position. |
Loosing the screw to make the adjustment. |
Note: The air flow meter does NOT need to be removed from the truck in order to perform these modifications, this was only done for illustration purposes.
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