Throttle Positioner System Toyota Tercel L30

DESCRIPTION

The Throttle Positioner (TP) system controls exhaust emissions during deceleration by holding throttle plate at an above-idle position during deceleration. This aids in complete burning of the air/fuel mixture.

System consists of Throttle Positioner (TP), Vacuum Transmitting Valve (VTV), Thermostatic Vacuum Switching Valve (TVSV), Vacuum Switching Valve (VSV) and jet assembly. Components may vary due to model application. The TP may be a single or a double diaphragm. System is controlled by engine vacuum. Engine operating temperature is used to control the various components. (Scheme 70)and (Scheme 71).

Scheme 70

Scheme 71

Scheme 72

Scheme 73

Scheme 74

Scheme 75

Scheme 76

Scheme 77

VACUUM TRANSMITTING VALVE (VTV)

Blow air through each side of valve. Air should pass freely from side "B" to side "A". (Black to Brown or Gray side) but be restricted from side "A" to "B" (Brown or Gray to Black side). (Scheme 76)

Scheme 78

Scheme 79

1. Drain coolant and remove TVSV. Place threaded end of valve in ice water with thermometer.
2. With temperature below 45°F (7°C), check that air passes from pipe "A" to pipe "B" and "E", and from pipe "C" to "D". (Scheme 77)
3. Heat water to 63-122°F (17-50°C). Check that air passes from pipe "C" to "D" and "E", and from pipe "A" to "B".
4. Continue heating water to above 154°F (68°C). Check that air passes from pipes "C" to "B" and "E" and does not flow from pipe "A" to any other pipe. If problem is found, replace TVSV.

TP DIAPHRAGMS

Verify that linkage moves properly as vacuum is applied. Replace assembly if linkage does not move.

JET

Blow through each port area of jet. Replace jet if air does not pass freely from both port areas.

Tercel Sedan

1. Apply battery voltage to VSV terminals. Blow through port "A" and note that air passes from port "B". Disconnect battery and repeat procedure. Air should not pass from port "B". (Scheme 81)
2. Note "+" terminal location. (Scheme 81) Connect ohmmeter to "+" terminal and valve body. Replace valve if continuity exists. Using ohmmeter, measure resistance between valve terminals. Resistance should be 38-44 ohms at 68°F (20°C). Replace valve if not within specification.

Scheme 80

Scheme 81

1. Warm engine to normal operating temperature. Check idle speed and adjust if necessary. Disconnect hose from TVSV "M" port and plug "M" port. (Scheme 73) This disconnects choke opener and EGR system.
2. Disconnect and plug vacuum hose from TP. (Scheme 74) Engine speed should now be 1400 RPM on Tercel Wagon models and 900 RPM on Corolla models. If not within specification, rotate adjusting screw to obtain correct engine speed. (Scheme 74) NOTE: Engine speed should be adjusted with cooling fan off.
3. Reconnect vacuum hose to TP. Check that engine returns to idle speed within 2-6 seconds. Reconnect TVSV "M" port vacuum hose. If no problem exists, system is okay.

Scheme 82

Scheme 83

Scheme 84

Scheme 85

1. Warm engine to normal operating temperature. Check idle speed and adjust if necessary. On Corolla FX models, disconnect hose from TVSV "M" port and plug "M" port. (Scheme 73) This disconnects choke opener and EGR system.
2. On Tercel Sedan models, disconnect and plug hose from EGR valve. (Scheme 75) On all models, disconnect diaphragm "A" vacuum hose from TP. (Scheme 74)
3. Ensure TP is positioned on the first step. Note engine speed. Adjust engine speed if not within specification. See «TP ENGINE SPEED SPECIFICATIONS»(/toyota/tercel/l30-1986-1990/remont/testing-diagnostics/#throttle-positioner-system) table. If not within specification, rotate adjusting screw to obtain correct engine speed. (Scheme 74) NOTE: Engine speed should be adjusted with cooling fan off.
4. On Tercel Sedan models, reconnect diaphragm "A" hose. On all models, disconnect and plug diaphragm "B" vacuum hose.
5. Ensure TP is positioned on the second step. Note engine speed. Engine speed should be within specification. See «TP ENGINE SPEED SPECIFICATIONS»(/toyota/tercel/l30-1986-1990/remont/testing-diagnostics/#throttle-positioner-system) table. On all models, reconnect diaphragm "B" vacuum hose and check that engine returns to idle speed within 2-6 seconds.
6. On Tercel Sedan models, reconnect EGR valve hose. On Corolla FX models, reconnect diaphragm "A" and TVSV vacuum hoses. If no problem exists, system is okay.

TP ENGINE SPEED

TP ENGINE SPEED SPECIFICATIONS

See also:
• TP ENGINE SPEED SPECIFICATIONS