Engine Controls - System/component Tests - 3.4L: Other Toyota Tacoma I

Power & Ground Circuits

For testing of Engine Control Module (ECM) power and ground circuits, see PIN VOLTAGE CHARTS - 3.4L article. See ECM LOCATION table for identifying ECM mounting locations.

ECM LOCATION

AIRFLOW METER

Note. Airflow meter may be referred to as Mass Airflow (MAF) meter.

1. Turn ignition off. Disconnect electrical connector from airflow meter. Airflow meter is located between air intake hose and upper cap on air cleaner assembly. Remove airflow meter and note airflow meter terminal identification. (Scheme 91)
2. Using ohmmeter, check resistance between terminals E2 and THA. Resistance should be within specification in relation to the temperature. See «AIRFLOW METER RESISTANCE»(ref-22481-S06322833382001010300000) table. Replace airflow meter if resistance is not within specification.
3. To test airflow meter operation, ensure electrical connector is installed on airflow meter. Connect voltmeter leads to proper terminals on airflow meter with electrical connector installed. (Scheme 92)
4. Turn ignition on. Apply air into airflow meter and note voltage reading. (Scheme 92) While air is being applied, voltage reading should fluctuate. Replace airflow meter if voltage does not fluctuate. Remove voltmeter.

AIRFLOW METER RESISTANCE

Scheme 91

Scheme 92

CAMSHAFT POSITION SENSOR

For testing camshaft position sensor, see CAMSHAFT POSITION SENSOR under IGNITION CHECKS (DISTRIBUTORLESS IGNITION SYSTEM) in BASIC TESTING - 3.4L article.

CRANKSHAFT POSITION SENSOR

For testing crankshaft position sensor, see CRANKSHAFT POSITION SENSOR under IGNITION CHECKS (DISTRIBUTORLESS IGNITION SYSTEM) in BASIC TESTING - 3.4L article.

2WD All Vehicles & 4WD Regular Cab

1. Remove EGR gas temperature sensor. EGR gas temperature sensor is screwed into side of EGR valve.
2. Place threaded end of EGR gas temperature sensor and thermometer in container of oil. Attach ohmmeter between electrical terminals on EGR gas temperature sensor.
3. Heat oil and note resistance at specified temperature. See «EGR GAS TEMPERATURE SENSOR RESISTANCE»(ref-22481-S23963763382001010300000) table. Replace EGR gas temperature sensor if resistance is not within specification. Reinstall EGR gas temperature sensor.

EGR GAS TEMPERATURE SENSOR RESISTANCE

ENGINE COOLANT TEMPERATURE (ECT) SENSOR

1. Ensure ignition is off. Disconnect electrical connector from ECT sensor. See «ENGINE COOLANT TEMPERATURE (ECT) SENSOR LOCATION»(ref-22481-S07635793232001010300000) table. To verify wire colors for proper sensor identification, see appropriate wiring diagram in «WIRING DIAGRAMS - 3.4L»(ref-22483) article. NOTE: The ECT sensor may be also identified using appropriate illustration in «THEORY/OPERATION - 3.4L»(ref-22482) article.
2. Drain cooling system and remove ECT sensor. Place probe end of ECT sensor and thermometer in container of water. Attach ohmmeter between electrical terminals on ECT sensor. Heat water and note that resistance is within specification in relation to temperature. (Scheme 93) Replace ECT sensor if resistance is not within specification.

ENGINE COOLANT TEMPERATURE (ECT) SENSOR LOCATION

Scheme 93

HEATED OXYGEN SENSOR

1. Two heated oxygen sensors are used. A heated oxygen sensor is used on exhaust pipe in front of catalytic converter. This oxygen sensor is referred to as front oxygen sensor or bank No. 1 sensor No. 1. Another heated oxygen sensor is located on exhaust pipe behind catalytic converter. This oxygen sensor is referred to as rear oxygen sensor or bank No. 1 sensor No. 2.
2. If problem exists with heated oxygen sensor, a diagnostic trouble code will be stored in Engine Control Module (ECM). For diagnostic trouble code diagnosis, see «TESTS W/CODES - 3.4L»(ref-22484) article.
3. To test heater on heated oxygen sensor, disconnect electrical connector from appropriate heated oxygen sensor and note heated oxygen sensor terminals. (Scheme 94)
4. On all heated oxygen sensors, use ohmmeter to check resistance between heated oxygen sensor terminals +B and HT. (Scheme 94) Replace heated oxygen sensor if resistance is not within specification. See «OXYGEN SENSOR HEATER RESISTANCE»(ref-22481-S26680321652001010300000) table.

OXYGEN SENSOR HEATER RESISTANCE

Scheme 94

KNOCK SENSORS

1. Knock sensors No. 1 and 2 are located below intake manifold on the cylinder block. (Scheme 95) Manufacturer recommends removing knock sensor from cylinder block before testing. See KNOCK SENSOR under ENGINE SENSORS & SWITCHES in «REMOVE/INSTALL/OVERHAUL - 3.4L»(ref-22488) article.
2. Using ohmmeter, check that no continuity exists between electrical terminal on knock sensor and body of knock sensor. Replace knock sensor if continuity exists.

Scheme 95

A/T

If problem exists with Park/Neutral Position (PNP) switch or circuit, a diagnostic trouble Code P1780 will be stored in the Engine Control Module (ECM). See TESTS W/CODES - 3.4L article for accessing diagnostic trouble codes.

1. Disconnect electrical connector from Park/Neutral Position (PNP) switch. PNP switch is mounted on side of transmission/transaxle. Note terminal identification. (Scheme 96)
2. Using ohmmeter, check for continuity between specified terminals with shift lever in proper positions. See «PARK/NEUTRAL POSITION SWITCH SPECIFICATIONS»(ref-22481-S27652700092001010300000) table. If proper continuity cannot obtained, adjust or replace switch as necessary.

PARK/NEUTRAL POSITION SWITCH SPECIFICATIONS

Scheme 96

THROTTLE POSITION SENSOR

1. Ensure ignition is off. Disconnect electrical connector from Throttle Position (TP) sensor mounted on side of throttle body. Note terminal identification on TP sensor. (Scheme 97)
2. Apply vacuum to throttle opener. Using ohmmeter, check resistance between specified terminals in relation to throttle position. See «THROTTLE POSITION SENSOR RESISTANCE»(ref-22481-S17994904512001010300000) table. Replace components as necessary if resistance is not within specification.

Scheme 97

THROTTLE POSITION SENSOR RESISTANCE (1)

VAPOR PRESSURE SENSOR

For testing of vapor pressure sensor, see FUEL EVAPORATION SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS.

VEHICLE SPEED SENSOR

1. Vehicle speed sensor is located on rear of combination meter in instrument cluster. Connect ohmmeter between terminals "A" and "B" on rear of combination meter. Terminals are located near vehicle speed sensor. (Scheme 98)or (Scheme 99).
2. Rotate speedometer cable shaft and note reading. Ohmmeter should deflect from continuity to no continuity 4 times per revolution of speedometer cable shaft. Replace speedometer if reading does not deflect as specified.

Scheme 98

Scheme 99

4WD SWITCH

1. The 4WD switch is located on side of transfer case and contains a Gray 2-pin electrical connector. Remove 4WD switch from transfer case. Connect ohmmeter between electrical terminals on 4WD switch.
2. Push pin on end of 4WD switch inward and ensure continuity exists. No continuity should exist when pin is released (outward) position. Replace 4WD switch if defective.

CIRCUIT OPENING RELAY

1. Ensure ignition is off. Remove circuit opening relay. See «CIRCUIT OPENING RELAY LOCATION»(ref-22481-S31737038382001010300000) table. (Scheme 100) CIRCUIT OPENING RELAY LOCATION Application Relay Location 3.4L Behind Lower Instrument Panel Cover, Next To Driver's Side Of Steering Column
2. To test circuit opening relay continuity, use ohmmeter to check continuity between specified terminals. (Scheme 101)
3. To test circuit opening relay operation, apply battery voltage and ground to relay and use ohmmeter to check continuity between specified terminals. (Scheme 101) Replace circuit opening relay if defective.

Scheme 100

EFI MAIN RELAY

Note. EFI main relay may also be referred to as EFI relay.

1. Ensure ignition is off. Remove EFI main relay from relay box at driver's side front corner of engine compartment, near battery.
2. To test EFI main relay continuity, use ohmmeter to check continuity between specified terminals. (Scheme 101)and (Scheme 102).
3. To test EFI main relay operation, apply battery voltage and ground to relay and use ohmmeter to check continuity between specified terminals. (Scheme 101)and (Scheme 102). Replace EFI main relay if defective.

Scheme 101

Scheme 102

See CIRCUIT OPENING RELAY under RELAYS.

See EFI MAIN RELAY under RELAYS.

Fuel Pump Pressure

For fuel pump pressure testing, see BASIC TESTING - 3.4L article.

Fuel Injectors

1. Ensure ignition is off.
2. Disconnect electrical connector at fuel injector. Using ohmmeter, measure resistance between electric terminals on fuel injector. Replace fuel injector if resistance is not 13.8 ohms at 68°F (20°C).
3. To check fuel injector volume, remove fuel injector. See FUEL RAILS & FUEL INJECTORS under FUEL SYSTEM in «REMOVE/INSTALL/OVERHAUL - 3.4L»(ref-22488) article. NOTE: Fuel injector is connected between fuel pressure regulator on the delivery pipe and fuel inlet pipe.
4. Disconnect fuel line from fuel inlet pipe and use Delivery Hose (09268-41046) to install fuel injector between fuel pressure regulator on delivery pipe and fuel inlet pipe. (Scheme 103)
5. Place fuel injector into a clean graduated container. Place vinyl tube on end of fuel injector to prevent fuel spillage.
6. Use scan tool to operate the fuel pump to pressurize the fuel system. See FUEL PRESSURE under FUEL SYSTEM in «BASIC TESTING - 3.4L»(ref-22485) article. NOTE: Fuel pump may also be operated to pressurize fuel system by applying battery voltage to electrical terminals on fuel pump. For operating of fuel pump, see FUEL PUMP RESISTANCE & OPERATION under «FUEL DELIVERY»(ref-22481-S02631504642001010300000) under FUEL SYSTEM.
7. Connect Fuel Injector Tester (09842-30070) to fuel injector for 15 seconds. (Scheme 104) Measure fuel injector volume. Test each fuel injector 2-3 times. Replace fuel injector if fuel injector volume is not within specification. See «FUEL INJECTOR VOLUME SPECIFICATIONS»(ref-22481-S37308994842001010300000) table. NOTE: Ensure difference between fuel injector volume on all fuel injectors is within specification. See FUEL INJECTOR VOLUME SPECIFICATIONS table.
8. Disconnect fuel injector tester. Ensure fuel leakage from end of fuel injector is one drop or less per one minute. Replace fuel injector if leakage exceeds specification. Remove test equipment.

FUEL INJECTOR VOLUME SPECIFICATIONS

Scheme 103

Scheme 104

Fuel Cut System

1. When testing fuel cut system, monitor engine RPM using scan tool. Connect scan tool to data link connector No. 3 for monitoring engine RPM. For connecting of scan tool, see appropriate application under IDLE SPEED & MIXTURE in «ADJUSTMENTS - 3.4L»(ref-22480) article.
2. Start and warm engine to normal operating temperature. Ensure A/C and all accessories are off. Gradually increase engine RPM to at least 3500 RPM.
3. Using stethoscope, check for fuel injector operating sound. Ensure when throttle lever is released, fuel injector stops operating momentarily and then resumes operating (fuel return RPM).
4. Ensure fuel return RPM is within specification. See «FUEL CUT SYSTEM SPECIFICATIONS»(ref-22481-S38538673282001010300000) table. Shut engine off. Remove test equipment.

FUEL CUT SYSTEM SPECIFICATIONS (1)

IDLE AIR CONTROL (IAC) VALVE

1. Start and warm engine to normal operating temperature. Ensure idle speed is within specification. See IDLE SPEED & MIXTURE in «ADJUSTMENTS - 3.4L»(ref-22480) article.
2. Shut engine off. Apply parking brake and place transmission/transaxle in Neutral. Ensure A/C is off. Install Jumper Wire (SST 09843-18020) between terminals TE1 and E1 on data link connector No. 1 located in the engine compartment. (Scheme 105) Start engine and note engine RPM.
3. Engine RPM should increase to 1000 RPM for 5 seconds and then return to idle. If engine RPM is not within specification, test IAC valve resistance and IAC valve operation. If engine RPM is within specification, remove jumper wire. Turn ignition off.
4. To test IAC valve resistance, ensure ignition is off. Disconnect electrical connector from IAC valve. IAC valve is located on lower area of throttle body. Using ohmmeter, checking resistance between +B terminal and each remaining terminal on IAC valve. (Scheme 106)
5. Replace IAC valve if resistance is not within specification. See «IAC VALVE RESISTANCE»(ref-22481-S32766660562001010300000) table. IAC VALVE RESISTANCE Application Ohms Cold (1) 17.0-24.5 Hot (2) 21.5-28.5 (1) Cold is with temperature of 14-122°F (-10-50°C). (2) Hot is with temperature of 122-212°F (50-100°C).
6. To test IAC valve operation, remove IAC valve from throttle body. Apply battery voltage to +B terminal on IAC valve. Apply battery ground to proper terminal and ensure valve opens and closes. (Scheme 107) Replace IAC valve if defective.
7. If IAC valve resistance is within specification and operates correctly, check wiring circuit between Engine Control Module (ECM) and IAC valve. See «ECM LOCATION»(ref-22481-S21182766622001010300000) table. See appropriate wiring diagram in «WIRING DIAGRAMS - 3.4L»(ref-22483) article.

ECM LOCATION

Scheme 105

Scheme 106

Scheme 107

IGNITION SYSTEM

Note. For basic ignition checks, see BASIC TESTING - 3.4L article.

Knock Sensor

See KNOCK SENSOR under ENGINE SENSORS & SWITCHES.

2WD Vehicles & 4WD W/Regular Cab

1. Ensure EGR vacuum modulator filter is clean and in good condition. Clean filter with compressed air (if necessary). NOTE: EGR vacuum modulator filter must be installed with coarse side facing upward, away from EGR vacuum modulator.
2. Using 3-way connector, install vacuum gauge in line with vacuum hose on top of EGR valve. Start engine. Ensure engine runs and idles smoothly to ensure proper seating of EGR valve.
3. Install Jumper Wire (SST 09843-18020) between terminals TE1 and E1 on data link connector No. 1 located in engine compartment. (Scheme 105)
4. Operate engine at 2800 RPM with engine coolant temperature less than 113°F (45°C). No vacuum reading should be obtained. EGR pipe should not be hot.
5. Warm engine so engine coolant temperature is greater than 176°F (80°C). Operate engine at 2800 RPM again. Ensure a low vacuum reading is now obtained.
6. Disconnect vacuum hose from port "R" on EGR vacuum modulator. (Scheme 108) Using additional hose, connect port "R" on EGR vacuum modulator directly to intake manifold. High vacuum reading should be obtained with engine at 3500 RPM. NOTE: Engine should misfire due to large amounts of exhaust gas being injected into intake manifold.
7. Shut engine off. Remove vacuum hose, vacuum gauge and reconnect original vacuum hoses. Remove jumper wire from data link connector No. 1.
8. To test EGR valve operation, remove and plug vacuum hose located on top of EGR valve. Start engine. Using vacuum pump, apply vacuum directly to EGR valve with engine idling. Engine should run rough or stall. If EGR system does not operate as described, each individual component should be tested. Shut engine off.

Scheme 108

Scheme 109

EGR GAS TEMPERATURE SENSOR

See EGR GAS TEMPERATURE SENSOR TESTING under ENGINE SENSORS & SWITCHES.

EGR VACUUM MODULATOR

Note. When testing EGR vacuum modulator, it may be necessary to monitor engine RPM by using scan tool. For scan tool connections, see IDLE SPEED & MIXTURE in ADJUSTMENTS - 3.4L article.

1. Mark vacuum hose locations and disconnect vacuum hoses from EGR vacuum modulator. (Scheme 109) Block ports "P" and "R" on EGR vacuum modulator. (Scheme 108) NOTE: Ports "P" and "R" are the double ports on side of EGR vacuum modulator. Port "Q" is single port on side of EGR vacuum modulator.
2. Apply air pressure to port "Q". (Scheme 108) Air should flow freely through air filter side of EGR vacuum modulator.
3. Start and operate engine at 3500 RPM. Repeat test procedures in steps 1) and 2). Strong resistance of airflow should be felt. Replace EGR vacuum modulator if strong resistance is not felt. Reconnect vacuum hoses to proper locations.

1. Remove EGR VSV. (Scheme 109) Using ohmmeter, ensure continuity exists between electrical terminals on EGR VSV and resistance is 33-39 ohms at 68°F (20°C). Replace EGR VSV if no continuity exists or resistance is not within specification.
2. Using ohmmeter, ensure no continuity exists between each electrical terminal and body of EGR VSV. Replace EGR VSV if continuity exists between electrical terminal and body of EGR VSV.
3. To test EGR VSV operation, apply air pressure to port "E". Ensure air flows from port "G" and not from the filter. Perform STEP 1. (Scheme 110)
4. Apply battery voltage and ground to electrical terminals on EGR VSV. Apply air pressure to port "E". Ensure air flows from filter and not from port "G". Perform STEP 2. (Scheme 110) Replace EGR VSV if defective. Reinstall EGR VSV.

Scheme 110

FUEL EVAPORATION SYSTEM

Note. Fuel evaporation systems contain different components depending on application. (Scheme 109) When testing fuel evaporation system components, use illustration to determine component location.

Charcoal Canister

1. Remove charcoal canister. Remove Vacuum Switching Valves (VSV) from top of charcoal canister.
2. Install plugs on ports "A" and "B". (Scheme 111) Check for clogged filter and/or stuck check valve or diaphragm by applying light air pressure to port "D" while holding port "C" closed. (Scheme 111) Ensure air flows freely from port "E".
3. Apply light air pressure to port "D" while holding ports "C" and "E" closed. (Scheme 111) Ensure no air flows from port "F".
4. Using vacuum pump, apply light vacuum to port "C". Ensure vacuum does not decrease when port "F" is closed, and that vacuum decreases with port "F" is opened.
5. While holding port "F" closed, use vacuum pump to apply light vacuum to port "D". Ensure vacuum does not decrease when port "C" is closed, and that vacuum decreases with port "C" is opened. Remove plugs. Replace charcoal canister if defective.

Scheme 111

EVAP Vacuum Switching Valve

1. Remove EVAP Vacuum Switching Valve (VSV). See «EVAP VSV LOCATIONS»(ref-22481-S15398964762001010300000) table. (Scheme 109) EVAP VSV LOCATIONS Application Location 3.4L On End Of Charcoal Canister & Contains Black 2-Pin Electrical Connector NOTE: EVAP VSV may also be identified by wire colors. See appropriate wiring diagram in «WIRING DIAGRAMS - 3.4L»(ref-22483) article.
2. Using ohmmeter, ensure continuity exists between electrical terminals on EVAP VSV and resistance is within specification. See «EVAP VSV RESISTANCE»(ref-22481-S33232649112001010300000) table. Replace EVAP VSV if no continuity exists or resistance is not within specification. EVAP VSV RESISTANCE Application Ohms @ 68°F (20°C) 3.4L 30-34
3. Using ohmmeter, ensure no continuity exists between each electrical terminal and body of EVAP VSV. Replace EVAP VSV if continuity exists between electrical terminal and body of EVAP VSV.
4. To test EVAP VSV operation, apply air pressure to port "E". Ensure no air flows from port "F". Perform STEP 1. (Scheme 112)
5. Apply battery voltage and ground to electrical terminals on EVAP VSV. Apply air pressure to port "E". Ensure air flows from port "F". Perform STEP 2. (Scheme 112) Replace EVAP VSV if defective.

Scheme 112

1. Ensure ignition is off. To test vapor pressure sensor supply voltage, disconnect electrical connector from vapor pressure sensor. (Scheme 109) See «VAPOR PRESSURE SENSOR LOCATION»(ref-22481-S39141579542001010300000) table. VAPOR PRESSURE SENSOR LOCATION Application Location 3.4L On Firewall, Above Brake Booster & Contains Black 3-Pin Electrical Connector
2. Turn ignition on. Using voltmeter, measure voltage between terminals VC and E2 on wiring harness side of electrical connector for vapor pressure sensor. The VC and E2 terminals are the 2 outer terminals. DO NOT use center terminal. Supply voltage should be 4.5-5.5 volts.
3. If supply voltage is not within specification, check wiring circuit. See appropriate wiring diagram in «WIRING DIAGRAMS - 3.4L»(ref-22483) article. If supply voltage is within specification, turn ignition off. Reinstall electrical connector on vapor pressure sensor.
4. To test vapor pressure sensor output voltage, turn ignition on. Disconnect vacuum hose from vapor pressure sensor. Obtain access to Engine Control Module (ECM). See «ECM LOCATION»(ref-22481-S21182766622001010300000) table. ECM LOCATION Model Location 3.4L Behind Glove Box
5. Connect voltmeter between specified terminals on ECM. (Scheme 113)and (Scheme 114). See «ECM TERMINAL APPLICATION»(ref-22481-S11363176142001010300000) table. ECM TERMINAL APPLICATION Application & Terminal No. Wire Color A/T 15 Red/Yellow 22 Brown/Black M/T 4 Red/Yellow 9 Brown/Black
6. Using vacuum pump, apply.59 in. Hg of vacuum to vapor pressure sensor. Ensure output voltage is within specification. See «VAPOR SENSOR OUTPUT VOLTAGE»(ref-22481-S07632095372001010300000) table.
7. Release vacuum from vapor pressure sensor. Ensure output voltage is within specification. See «VAPOR SENSOR OUTPUT VOLTAGE»(ref-22481-S07632095372001010300000) table.
8. Apply.22 psi (.015 kg/cm 2 ) to vapor pressure sensor. Ensure output voltage is within specification. See «VAPOR SENSOR OUTPUT VOLTAGE»(ref-22481-S07632095372001010300000) table. Replace vapor sensor if output voltage is not within specification. Reconnect vacuum hose.

VAPOR SENSOR OUTPUT VOLTAGE

Scheme 113

Scheme 114

Vapor Pressure Sensor Vacuum Switching Valve

1. Remove vapor pressure sensor Vacuum Switching Valve (VSV). Vapor pressure sensor VSV is located on charcoal canister. (Scheme 109)
2. Using ohmmeter, ensure continuity exists between electrical terminals on vapor pressure sensor VSV and resistance is within specification. See «VAPOR PRESSURE SENSOR VSV RESISTANCE»(ref-22481-S29633854262001010300000) table. Replace vapor pressure sensor VSV if no continuity exists or resistance is not within specification. VAPOR PRESSURE SENSOR VSV RESISTANCE Application Ohms @ 68°F (20°C) 3.4L 37-44
3. Using ohmmeter, ensure no continuity exists between each electrical terminal and body of vapor pressure sensor VSV. Replace vapor pressure sensor if continuity exists between electrical terminal and body of vapor pressure sensor VSV.
4. To test vapor pressure sensor VSV operation, apply air pressure to port "E". Ensure air flows from port "G" and not from port "F". Perform STEP 1. (Scheme 115)
5. Apply battery voltage and ground to electrical terminals on vapor pressure sensor VSV. Apply air pressure to port "E". Ensure air flows from port "F" and not from port "G". Perform STEP 2. (Scheme 115) Replace vapor pressure sensor VSV if defective.

Scheme 115

POSITIVE CRANKCASE VENTILATION (PCV)

1. Remove PCV valve. Apply air pressure to PCV valve at cylinder head side of PCV valve. Ensure air flows easily through PCV valve.
2. Apply air pressure to PCV valve at intake manifold side of PCV valve. Ensure air flows through PCV valve with some resistance.
3. Apply air pressure to PCV valve at intake manifold side of PCV valve. Using small screwdriver, push upward on valve located inside PCV valve, at cylinder head side of PCV valve. Ensure air flows through PCV valve with strong resistance. Replace PCV valve if valve does not function as described.

With M/T

1. Start and warm engine to normal operating temperature. Ensure idle speed is within specification. See IDLE SPEED & MIXTURE in «ADJUSTMENTS - 3.4L»(ref-22480) article. Shut engine off. Remove cap, filter and separator from dashpot on throttle body. (Scheme 116)
2. Start engine. Maintain engine speed at 2500 RPM. Plug Vacuum Transmitting Valve (VTV) hole in dashpot with your finger. (Scheme 117)
3. Release throttle. Dashpot should be extended and dashpot setting RPM should be 1800-2200 RPM. If dashpot setting RPM is not within specification, rotate dashpot adjusting screw to obtain correct RPM. (Scheme 118)
4. Repeat step 3) to ensure proper adjustment is obtained. To check operation of Vacuum Transmitting Valve (VTV), operate engine at 2500 RPM with finger placed over VTV hole in dashpot.
5. Release throttle. Remove finger from VTV hole in dashpot. Ensure engine returns to proper idle speed in approximately one second. Install separator, filter and cap. Ensure filter is installed with the coarse surface facing outward (away from dashpot).

Scheme 116

Scheme 117

Scheme 118

THROTTLE OPENER

1. Start and warm engine to normal operating temperature. Ensure idle speed is within specification. See IDLE SPEED & MIXTURE in «ADJUSTMENTS - 3.4L»(ref-22480) article.
2. Shut engine off. Disconnect and plug vacuum hose at throttle opener. (Scheme 119) Start engine and note engine speed. Engine speed should be 900-1950 RPM.
3. If engine speed is not within specification, replace throttle body. Shut engine off. Reinstall vacuum hose on throttle opener. Start engine and ensure engine returns to proper idle speed.

Scheme 119