Toyota EFI Mixture Adjustment
06-30-2006, 02:57 AM
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Toyota EFI Mixture Adjustment
For all those folks who are constantly griping about running lean...this is for Toyota cars specifically but can be adapted for trucks:
Toyota EFI Mixture Adjustment
The following is courtesy of Pat Braden.
It is a modification that allows adjustment of the Air/Fuel Ratio on Toyota's equipped with EFI
Follow these steps:
1. Locate the water temperature sensor. On MR2's and FX16's the sensor is located on the water neck at the rear of the engine. On Celica's Supra's and GT-S Corolla's, the sensor is located on the thermostat housing on the front of the engine: just follow the upper radiator hose to the housing. The sensor is bright green with a rectangular base and has a two-prong plug with a rubber boot.
2. With the engine off, disconnect the plug and unwrap the plastic tape at the rear of the boot. Pull the boot forward to expose the two wires under the boot. There should be a brown wire and a green wire (sometimes green with a white stripe). You want to tap into the green wire. You may do it here or by the computer. It is preferable to tap into the wire by the computer. You can trace the wire using an ohmmeter only if you disconnect the multi-plug containing the wire at the computer. See your shop manual for the location of the computer in your car.
3. Locate and cut the green (or green and white) wire and splice a 0-2,000 ohm linear (not logarithmic) variable resistor (also called a potentiometer) with a 1.25 watt capacity in series with the water temperature sensor. The resistor can be purchased at any electronic store.
4. When wiring the resistor there will be three prongs coming out of the resistor body. You will want to use the center prong and one of the side ones. Attaching the wire to one of the side prongs will cause the resistance to increase when the knob is turned clockwise. The other prong will cause the resistance to increase when the knob is turned counterclockwise.
If you mount the resistor in the dash, you'll be able to adjust the mixture while you drive. Use fourteen-gauge stranded wire to install the resistor and put some kind of pointer on the resistor knob to indicate it's optimum position.
5. Determine the optimum position by adjusting the resistor until rpm increases slightly. If the engine chokes, sputters and smokes or if the "check engine" light comes on, it's too rich. Back off a little. You should feel a big difference between on and off. Note: A rich/lean gauge can be used to set the optimum point.
Toyota EFI Mixture Adjustment
The following is courtesy of Pat Braden.
It is a modification that allows adjustment of the Air/Fuel Ratio on Toyota's equipped with EFI
Follow these steps:
1. Locate the water temperature sensor. On MR2's and FX16's the sensor is located on the water neck at the rear of the engine. On Celica's Supra's and GT-S Corolla's, the sensor is located on the thermostat housing on the front of the engine: just follow the upper radiator hose to the housing. The sensor is bright green with a rectangular base and has a two-prong plug with a rubber boot.
2. With the engine off, disconnect the plug and unwrap the plastic tape at the rear of the boot. Pull the boot forward to expose the two wires under the boot. There should be a brown wire and a green wire (sometimes green with a white stripe). You want to tap into the green wire. You may do it here or by the computer. It is preferable to tap into the wire by the computer. You can trace the wire using an ohmmeter only if you disconnect the multi-plug containing the wire at the computer. See your shop manual for the location of the computer in your car.
3. Locate and cut the green (or green and white) wire and splice a 0-2,000 ohm linear (not logarithmic) variable resistor (also called a potentiometer) with a 1.25 watt capacity in series with the water temperature sensor. The resistor can be purchased at any electronic store.
4. When wiring the resistor there will be three prongs coming out of the resistor body. You will want to use the center prong and one of the side ones. Attaching the wire to one of the side prongs will cause the resistance to increase when the knob is turned clockwise. The other prong will cause the resistance to increase when the knob is turned counterclockwise.
If you mount the resistor in the dash, you'll be able to adjust the mixture while you drive. Use fourteen-gauge stranded wire to install the resistor and put some kind of pointer on the resistor knob to indicate it's optimum position.
5. Determine the optimum position by adjusting the resistor until rpm increases slightly. If the engine chokes, sputters and smokes or if the "check engine" light comes on, it's too rich. Back off a little. You should feel a big difference between on and off. Note: A rich/lean gauge can be used to set the optimum point.
06-30-2006, 05:32 AM
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