INTRODUCTION
Before testing separate components or systems, perform procedures in BASIC TESTING article in the ENGINE PERFORMANCE Section. Since many computer-controlled and monitored components set a trouble code if they malfunction, also perform procedures in TESTS W/CODES article in the ENGINE PERFORMANCE Section.
Note. Testing individual components does not isolate shorts or opens. Perform all voltage tests with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure. Use ohmmeter to isolate wiring harness shorts or opens.
Note. When testing some systems, tachometer may be required. Tachometer must be connected to proper terminals. For tachometer connections, see IDLE SPEED & MIXTURE in ADJUSTMENTS article in the ENGINE PERFORMANCE Section.
Scheme 116
Scheme 117
- Using a 3-way connector, connect vacuum gauge to actuator valve. (Scheme 116) Start engine. With engine idling, ensure no vacuum reading is obtained.
- Fully open throttle, and ensure vacuum reading momentarily reads approximately 8 in. Hg and actuator valve rod pulls inward. If actuator valve rod does not pull inward, proceed to step 3).
- Disconnect vacuum hose from actuator valve. Using vacuum pump, apply approximately 8 in. Hg of vacuum to actuator valve. Ensure actuator valve rod pulls inward and remains pulled inward for at least one minute. Replace actuator valve if defective. If actuator valve operates correctly, reconnect vacuum hose and proceed to step 4).
- Disconnect vacuum hoses from vacuum tank, located near driver's side headlight in engine compartment. Apply air pressure to port "B" on vacuum tank and ensure air passes out port "A". (Scheme 117) Apply air pressure to port "A" and ensure air does not pass out port "B". (Scheme 117)
- Plug port "B" on vacuum tank. Using vacuum pump, apply approximately 8 in. Hg of vacuum to port "A". (Scheme 117) Ensure vacuum reading will hold for at least one minute. Replace vacuum tank if defective and recheck system operation. If vacuum tank is okay, reconnect vacuum hoses and proceed to step 6).
- Disconnect electrical connectors from IACV Vacuum Switching Valve (VSV), located near valve cover. (Scheme 118) Using ohmmeter, ensure continuity exists between electrical terminals on VSV. Check that no continuity exists between each electrical terminal and the body of the VSV.
- Apply air pressure to port "B" and ensure air passes out the filter. (Scheme 119) Connect battery voltage to VSV terminals. Apply air pressure to port "B" and ensure air passes out port "A". (Scheme 119) Replace VSV if defective and recheck system operation. If VSV is okay, proceed to step 8).
- Turn ignition on. Check for battery voltage at Black/Orange wire of VSV electrical connector. If battery voltage exists, replace Electronic Control Unit (ECU). If battery voltage does not exist, check EFI main relay. See EFI MAIN RELAY under RELAYS.
- If EFI main relay is okay, check wiring. See appropriate wiring diagram in WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section. Repair as necessary and recheck system operation.
