Idle Speed/Throttle Actuator - Mechanical: Testing and Inspection

3A-C & 4A-C ENGINES EXC. COROLLA FRONT WHEEL DRIVE
1. Run engine until it reaches operating temperature.
2. Check idle speed and adjust as necessary.
3. Ensure throttle positioner is released at idle.
4. On 3A-C and 4A-C engines, disconnect hose from second port from top of TVSV and plug the open port.
5. On all models, disconnect vacuum hose from throttle position diaphragm.
6. Ensure throttle positioner is set.
7. Ensure engine speed is within specifications, with throttle positioner set.
8. Adjust speed as necessary by turning throttle positioner adjusting screw.
9. Connect vacuum hoses.
10. Ensure engine returns to idle speed within 2---6 seconds on 4A-C engines, or 3---10 seconds on the other engines after connecting hose.
11. If test results are unsatisfactory, test individual components.

BI-METAL VACUUM SWITCHING VALVE
1. Drain coolant.
2. Remove bi-metal vacuum switching valve.
3. Using cool water, cool valve to below 104°F.
4. Blow air into either pipe and ensure air flows from other pipe.
5. Using hot water, heat valve to above 129°F.
6. Blow air into either pipe and ensure air does not flow from other pipe.
7. If air flow is not as described, replace valve.
8. Apply suitable sealer to valve threads and install valve.
9. Fill radiator with coolant.

DIAPHRAGMS
1. Ensure throttle positioner rod moves in conjunction with applied vacuum.
2. If throttle positioner rod does not move as described, replace diaphragm(s).

Fig. 39 Throttle position adjustment specifications:

THROTTLE POSITIONER, ADJUST
1. Start engine and run until it reaches normal operating temperature.
2. Connect tachometer following manufacturer's instructions, then adjust curb idle speed to specifications.
3. Disconnect vacuum hoses from throttle positioner. On Corolla front wheel drive (4A-C & 4A-LC engine), disconnect outer hose and adjust ``idle-up'' RPM, reconnect outer hose and disconnect inner hose, then adjust TP set RPM.
4. Adjust engine RPM to specifications.

Note: Ensure that electric cooling fan, if equipped, is off when performing adjustment.