Engine Controls - System/component Tests Toyota Corolla VI

INTRODUCTION

Note. Prior to testing separate components or systems, it is highly recommended that all procedures listed in BASIC TESTING be performed. Since many computer controlled and monitored components will set a trouble code if they malfunction, it is also recommended that self diagnosis be performed. See TESTS W/CODES .

Scheme 71

A/C SWITCH DESCRIPTION

Then the air conditioner is turned on, the ECU monitors the signal that turns on the compressor clutch. The ECU uses this signal for controlling idle speed during A/C operation.

AIRFLOW METER/SENSOR TEST

Turn ignition off. Unplug wiring connector from airflow meter. Note terminal identification. Using an ohmmeter, measure resistance between specified terminals. Replace airflow meter if not within specification. See AIRFLOW METER RESISTANCE SPECIFICATIONS table.

Scheme 72

Scheme 73

AIRFLOW METER RESISTANCE SPECIFICATIONS

Note. On 4WD (4A-FE), air temperature sensor is tested as part of airflow meter.

4WD AIR TEMP SENSOR TEST

Ensure ignition is off. Unplug air temperature sensor. Measure resistance across air temperature sensor terminals at specified temperature. (Scheme 74)

Scheme 74

COOLANT TEMP SENSOR TEST

1. Ensure ignition is off. Unplug connector from sensor. For sensor location, see appropriate illustration in THEORY/OPERATION article in this section.
2. Using ohmmeter, check resistance between sensor terminals. Replace sensor if resistance is not within specification at specified temperature.

Scheme 75

EGR GAS TEMP SENSOR TEST

Remove sensor from side of EGR valve. Place threaded end of sensor and thermometer in container of oil. Attach ohmmeter to sensor terminals. Heat the oil and note the resistance at specified temperature. See EGR TEMPERATURE SENSOR SPECIFICATIONS table. Replace sensor if not within specification.

EGR TEMPERATURE SENSOR SPECIFICATIONS

Scheme 76

NEUTRAL/START SWITCH CHECK

Unplug switch connector at transmission or transaxle. Note terminal identification. Using ohmmeter, check for continuity at specified terminals with gearshift in correct range. Refer to the NEUTRAL/START SWITCH SPECIFICATIONS table.

NEUTRAL/START SWITCH SPECIFICATIONS

Scheme 77

OXYGEN (O2) SENSOR FEEDBACK VOLTAGE TEST

1. Warm engine to normal operating temperature. Connect an analog type voltmeter to engine check connector "VF1" (or "VF") and "E1" terminals. To test oxygen sensor feedback voltage, follow procedures in the diagnostic flow chart in (Scheme 79).
2. If analog voltmeter does not respond correctly as described in (Scheme 79) diagnostic test procedure, O2 sensor can also be checked in conventional manner with digital volt/ohm meter (10 meg. ohm resistance). Attach DVOM to "OX" terminal of engine check connector under hood.
3. An O2 sensor going bad will have very few fluctuations on the analog voltmeter "VF" circuit, and the DVOM will remain near.50 volts on the "OX" circuit.
4. Depending on model application, some vehicles may be equipped with a main O2 sensor, sub-oxygen sensor and an O2 sensor heater. See «OXYGEN SENSOR APPLICATION»(/toyota/corolla/vi-1987-1993/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table.

OXYGEN SENSOR APPLICATION

Note. Trouble code Nos. 21, 25, 26 and 27 are O2 sensor circuit codes. Also check for coolant temperature sensor code No. 22. Faulty coolant temperature sensor could cause faulty O2 sensor readings.

Scheme 78

Scheme 79

SUB-OXYGEN SENSOR TEST

1. Inspection is required when trouble code No. 27 exists. Clear trouble codes. See CLEARING TROUBLE CODES under TESTS W/CODES article in this section. Warm engine to normal operating temperature. CAUTION: DO NOT exceed 62 MPH or trouble code will be cancelled.
2. Drive vehicle between 50 and 61 MPH for at least 5 minutes in 4th or 5th gear (Man. Trans.) or "D" range (Auto. Trans.).
3. Fully depress accelerator pedal for at least 10 seconds with engine RPM at least 3000 RPM.
4. Stop engine and turn ignition off. Repeat previous steps and note if trouble code No. 27 exists again. If trouble code exists again, check sub-oxygen sensor circuit for continuity, shorts or grounds. Replace sub-oxygen sensor if circuit is okay.

OXYGEN (O2) SENSOR HEATER TEST

1. Unplug O2 sensor connector. Using ohmmeter, measure resistance between sensor terminals. Replace sensor if resistance is not within 5-6 ohms at 68°F (20°C).
2. A trouble code No. 21 is also an indicator of a problem in O2 sensor circuit. Trouble code No. 21 will set if O2 sensor heater circuit opens or shorts to ground on "HT" wire from sensor to ECU.

Scheme 80

THROTTLE POSITION SENSOR (TPS) CHECK

Turn ignition off. Unplug electrical connector at TPS on throttle body. Note terminal identification. Insert specified thickness feeler gauge between throttle stop screw and throttle lever. See TPS RESISTANCE SPECIFICATIONS table. Using an ohmmeter, check for resistance or continuity. Replace or adjust TPS if not within specification.

TPS RESISTANCE SPECIFICATIONS

Scheme 81

Scheme 82

MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR - (4WD 4A-FE)

Note. Manifold Absolute Pressure (MAP) sensor is also known as Vacuum Sensor on 4WD (4A-FE).

1. Ensure ignition switch is off. Unplug vacuum sensor electrical connector. Sensor is on center of firewall.
2. Turn ignition on, with engine off. Measure voltage between both terminals of sensor harness. (Scheme 83) Voltage should be 4-6 volts. This is reference voltage from ECU. If voltage is not present or low, check wiring and ECU.
3. Turn ignition off. Plug in vacuum sensor electrical connector. To test vacuum sensor, disconnect vacuum sensor hose from intake chamber. Turn ignition on with engine off.
4. With ECU connectors in place, carefully connect digital (10 meg. resistance) voltmeter to back side of terminals "E2" and "PIM". (Scheme 84) Connect hand-held vacuum pump and gauge to sensor vacuum hose.
5. Measure voltage drop at specified vacuum reading. See the «MAP (VACUUM) SENSOR SPECIFICATIONS»(/toyota/corolla/vi-1987-1993/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. Replace sensor if defective.

MAP (VACUUM) SENSOR SPECIFICATIONS

Scheme 83

Scheme 84

VEHICLE SPEED SENSOR (VSS) - ANALOG TYPE

Remove combination meter from instrument cluster. Connect ohmmeter between terminals "A" and "B". (Scheme 85) Rotate meter shaft and note reading. Ohmmeter should deflect from 0 (zero) to infinity as shaft is rotated.

Scheme 85

CIRCUIT OPENING RELAY CHECK

The circuit opening relay is located near the ECU, under the center of dash, in front of the console. (Scheme 71) To check circuit opening relay (Scheme 86) The circuit opening relay is located under the center of the dash. Replace relay if defective.

Note. During cranking, there should be 12 volts present at "FP" terminal of circuit opening relay. This is the fuel pump (or fuel pump relay) line. See WIRING DIAGRAMS for wire color.

Scheme 86

Scheme 87

EFI MAIN RELAY TEST

To test EFI main relay (Scheme 88) The main EFI relay is located in the relay bank, on the left side of the fenderwell. Replace relay if defective.

Scheme 88

FUEL DELIVERY CHECK

For fuel pump pressure and fuel pressure regulator testing, see BASIC TESTING article in this section.

FUEL INJECTOR CHECK

1. Turn ignition off. Unplug each injector connector. Measure resistance across both terminals. Resistance should be 13.8 ohms at 68°F (20°C).
2. To check injector spray pattern and volume, relieve fuel system pressure and remove injectors from engine. Disconnect fuel hose from fuel filter outlet. Use Fuel Injection Kit (09268-41080) to tee fuel injector between fuel filter and fuel pressure regulator.
3. Place injector into a graduated container. Place vinyl tube on end of injector to prevent fuel from splashing out.
4. Hook up Fuel Injector Tester (09842-30070) or trigger box with appropriate resistor to fuel injector. Turn ignition on, with engine off.
5. Connect jumper wire to engine check connector terminals "FP" and "+B" to pressurize fuel system. For engine check connector locations see scheme 19 Connector terminals are marked on inside of check connector cover. Fuel pump check connector is 2-wire connector near airflow meter in left rear corner of engine compartment (White/Black and Green wires).
6. Trigger injector for 15 seconds. Measure volume and check spray pattern. Test each injector 2-3 times. Replace injector if volume is not as specified. See «FUEL INJECTOR VOLUME SPECIFICATIONS»(/toyota/corolla/vi-1987-1993/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. FUEL INJECTOR VOLUME SPECIFICATIONS Model Cu. In. (cc) 4WD 4A-FE 2.4-3.1 (40-50) 2WD 4A-GE 2.7-3.4 (45-55) Difference Between Each Injector.3 (5)
7. Disconnect injector trigger. Fuel leakage from end of injector should be one drop or less in one minute. (Scheme 90) Replace injector if leakage is more than specified.

Scheme 89

Scheme 90

FUEL PRESSURE-UP SYSTEM - 2WD (4A-GE)

1. Ensure coolant temperature sensor and air temperature sensor (in airflow meter) and circuits are operating correctly.
2. Fuel pressure-up system is controlled by ECU through a vacuum switching valve. The vacuum switching valve is fed current through the EFI main relay when the ignition is turned on. ECU controls the ground circuit. ECU will activate vacuum switching valve for 90-180 seconds when restarting engine at normal operating temperature.
3. Remove vacuum switching valve from vehicle. The fuel pressure-up vacuum switching valve is located on the lower side of the intake manifold runners. Check for continuity across valve wiring terminals. Resistance should be about 33-50 ohms at room temperature. There should be no continuity between each terminal and body of valve. To check operation (Scheme 91)

Scheme 91

DECELERATION FUEL-CUT SYSTEM

1. Connect a tachometer to engine (to monitor needle fluctuations). See ADJUSTMENTS article in this section for tachometer attaching points. Start engine and warm to operating temperature. Ensure A/C and other accessories are off.
2. Unplug throttle position sensor connector from throttle position sensor. Short terminals IDL and E1 (or E2) on wire side of connector. (Scheme 92)and (Scheme 93).
3. Gradually raise engine RPM. Fuel-cut operation can be checked by noting the fluctuation of tachometer needle. Fluctuation indicates fuel-cut system is being turned on and off. Check that fuel-cut points and fuel return points are within specifications. See the «DECELERATION FUEL-CUT & FUEL RETURN RPM»(/toyota/corolla/vi-1987-1993/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table.

Scheme 92

Scheme 93

DECELERATION FUEL-CUT & FUEL RETURN RPM

COLD START INJECTOR TEST

1. Cold start injector and cold start injector time switch are both fed current from ignition switch during cranking. Cold start injector ground circuit is controlled by cold start injector time switch. To test cold start injector, unplug cold start injector wiring harness. Check resistance between terminals of injector. Resistance should be 3-5 ohms. Replace injector if defective.
2. To check cold start injector spray pattern and leakage, relieve fuel system pressure. Remove cold start injector from vehicle.
3. Install fuel hose to injector. If original hose is too short, use Fuel Injection Kit (09268-41045) to extend the hose length and add a union. (Scheme 94)
4. Place container under cold start injector. Turn ignition on, with engine off. Connect jumper wire to engine check connector terminals "FP" and "+B" to pressurize fuel system. For engine check connector location (Scheme 96) Fuel pump check connector is 2-wire connector near airflow meter in left rear corner of engine compartment (White/Black and Green wires). CAUTION: Perform cold start injector connector test in shortest possible time.
5. Connect probes of Fuel Injector Tester (09842-30070) to battery. (Scheme 94) Connect other end of tester to cold start injector.
6. Ensure fuel spray is an even cone shape. Disconnect fuel injector tester harness and observe cold start injector. (Scheme 95) Maximum leakage should be one drop per minute with fuel pressure applied. Clean or replace cold start injector if defective.

Scheme 94

Scheme 95

Note. Cold start injector is controlled by cold start injector time switch when ignition switch is turned on. See the WIRING DIAGRAMS artticle in this section.

COLD START INJECTOR TIME SWITCH TEST

1. Unplug cold start injector time switch connector. For cold start injector time switch location, see the appropriate illustration in the THEORY/OPERATION article.
2. Using ohmmeter, check resistance between terminals "STA" & "STJ" at appropriate temperature. Refer to the «COLD START INJECTOR TIME SWITCH SPECIFICATIONS»(/toyota/corolla/vi-1987-1993/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. There should be continuity between terminal "STA" and ground. Replace switch if not within specification.

Note. "STA" terminal is fed current from ignition switch during cranking. "STJ" goes to cold start injector.

COLD START INJECTOR TIME SWITCH SPECIFICATIONS

Scheme 96

AUXILIARY AIR VALVE SYSTEM TEST

1. Engine must be cold to perform test. Install tachometer to engine. See ADJUSTMENTS article for tachometer attaching points.
2. Start engine. Turn idle speed adjusting screw to bottom of its travel. (Scheme 97) Engine RPM should drop slightly when coolant temperature is below 176°F (80°C).
3. Back out idle adjusting screw. Warm engine to normal operating temperature. Turn idle speed adjusting screw to bottom of its travel. Engine should idle roughly or die as idle speed adjusting screw is seated.
4. If engine RPM does not drop during step 2) or 3), check for vacuum leaks after the valve or restricted chamber in auxiliary air valve circuit. Replace valve if defective.

Scheme 97

IDLE-UP SYSTEM TEST - 4WD (4A-FE)

1. Ensure all accessories are switched off. Air control valve is powered by Black/Red wire from the EFI main relay. ECU controls valve ground.
2. Air control valve should be activated during cranking and for 10 seconds after engine starts. Check for battery voltage at air control valve during cranking and after engine starts. If voltage not present, check wiring from EFI main relay, and wiring to "V-ISC" terminal at ECU.
3. To check air control valve (Scheme 98)

Scheme 98

IDLE-UP SYSTEM TEST - 2WD (4A-GE)

1. Engine should be at normal operating temperature and all accessories off. Connect tachometer to engine. See ADJUSTMENTS for tachometer attachment points.
2. Start engine. After 10 seconds, engine RPM should drop about 100 RPM. With engine idling, watch tachometer for engine speed increase of about 100 RPM as each of the following electrical loads are switched on for a few seconds, and turned off. Brake Light Switch Defogger Switch Engine Cooling Fan Headlight Switch Heater Blower Switch
3. If any switch or component does not cause an increase of about 100 RPM, check for open circuit between switch and idle-up vacuum switching valve. If RPM does not increase with any switch turned on or components activated, check vacuum switching valve and circuit.
4. To check circuit, ensure all accessories are off. Check for battery voltage at vacuum switching valve connector during cranking and for 10 seconds after starting.
5. To check vacuum switching valve, remove vacuum switching valve from vehicle. The idle-up vacuum switching valve is located on the left shock tower. Air should not flow through vacuum switching valve ports. Connect 12 volts to one wire terminal on valve and ground other terminal. Air should flow through ports. (Scheme 99)

Scheme 99

IGNITION SYSTEM DIAGNOSTIC CODE TESTS

Note. ECU is programmed to detect ignition problems. Checking for trouble codes can speed up your diagnosis. If ECU detects a problem a diagnostic code will be set in memory. For information on system self-diagnostic capabilities and how to retrieve codes, see TESTS W/CODES article in this section.

CODE 12 (NO RPM SIGNAL)

ECU will store trouble code No. 12 in memory if it does not receive signal from either "NE" pick-up coil (RPM) or "G" pick-up coil (crank position) within 2 seconds of engine cranking.

CODE 13 (NO RPM SIGNAL)

ECU will store trouble code No. 13 in memory if it does not receive signal "NE" pick-up coil (RPM) when engine speed is above 1000 RPM.

CODE 14 (IGNITION SIGNAL PROBLEM)

ECU will store trouble code No. 14 in memory if it does not receive "IGF" (ignition detection) signal 6-8 times in succession.

SPARK TEST

1. On models with integral ignition coil, disconnect spark plug wires. Remove spark plugs. Install spark plugs to each spark plug wire. Ground spark plugs. Spark plug tester can also be used..
2. On models with an external ignition coil, disconnect high-tension (coil) wire from distributor. Hold wire about 1/2" away from ground. CAUTION: To prevent gasoline from being injected, do not crank engine for more than 2 seconds.
3. On all models, crank engine and check for spark. If spark does not occur, check ignition coil, ignitor and distributor connections.
4. If connections are good, check resistance of high-tension wires. If resistance is not within specification, replace wires. Resistance should be 25,000 ohms maximum per wire. If wires are okay, go to next step.
5. Check power supply to ignition coil and ignitor. Place ignition switch in "ON" position. Check for voltage at ignition coil positive terminal. If voltage is not present, check wiring between ignition switch, coil, and ignitor. If voltage is present, go to next step.
6. Check ignition coil resistance. See appropriate IGNITION COIL RESISTANCE TESTS in this article. If ignition coil resistance is not as specified, replace coil. If coil resistance is within specification, go to next step.
7. Check pick-up coil resistance. See «PICK-UP COIL RESISTANCE TEST»(/toyota/corolla/vi-1987-1993/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) in this article. If resistance is within specification, go to next step. If pick-up coil resistance is not as specified, replace pick-up coil. NOTE: On some models, it is necessary to replace entire distributor assembly.
8. Check air gap between reluctor and pick-up coil. Refer to «PICK-UP COIL AIR GAP CHECK»(/toyota/corolla/vi-1987-1993/remont/testing-diagnostics/#engine-controls-systemcomponent-tests__pick-up-coil-air-gap-check) in this article. If air gap is incorrect, replace distributor assembly.
9. If air gap is correct, check ignition "IGT" signal from ECU. See appropriate trouble code No. 14 chart in TESTS W/CODES article. If "IGT" signal is okay, replace ignitor.

PRIMARY COIL RESISTANCE TESTS

1. Disconnect ignition coil so it is isolated from remainder of system. Using ohmmeter, measure resistance between coil positive (+) and negative (-) terminals. (Scheme 100)or (Scheme 101).
2. If primary resistance is not within specification, replace ignition coil. See «IGNITION COIL RESISTANCE»(/toyota/corolla/vi-1987-1993/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. If resistance is within specification, proceed to SECONDARY COIL RESISTANCE.

Scheme 100

Scheme 101

IGNITION COIL RESISTANCE (1)

SECONDARY COIL RESISTANCE TESTS

1. Disconnect ignition coil so it is isolated from remainder of system. Using an ohmmeter, measure resistance between coil positive (+) terminal and coil tower. See «IGNITION COIL RESISTANCE»(/toyota/corolla/vi-1987-1993/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. (Scheme 102)or (Scheme 103).
2. If resistance is not within specification, replace ignition coil. If resistance is within specification, proceed to the «PICK-UP COIL RESISTANCE TEST»(/toyota/corolla/vi-1987-1993/remont/testing-diagnostics/#engine-controls-systemcomponent-tests).

Scheme 102

Scheme 103

4WD (4A-FE)

1. Measure pick-up coil resistance between terminals "G(+)" and "G(-)", and between "NE(+)" and "G(-)". Resistance should be 140-180 ohms when checked at room temperature.
2. If resistance is not within specification, replace distributor. See «PICK-UP COIL RESISTANCE»(/toyota/corolla/vi-1987-1993/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. If resistance is within specification, proceed to «PICK-UP COIL AIR GAP CHECK»(/toyota/corolla/vi-1987-1993/remont/testing-diagnostics/#engine-controls-systemcomponent-tests__pick-up-coil-air-gap-check) .

2WD (4A-GE)

1. Measure pick-up coil resistance between terminals "G(+)" and "G(-)", and between "NE(+)" and "NE(-)". Resistance should be 140-180 ohms when checked at room temperature.
2. If resistance is not within specification, replace distributor. See «PICK-UP COIL RESISTANCE»(/toyota/corolla/vi-1987-1993/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. If resistance is within specification, proceed to «PICK-UP COIL AIR GAP CHECK»(/toyota/corolla/vi-1987-1993/remont/testing-diagnostics/#engine-controls-systemcomponent-tests__pick-up-coil-air-gap-check) .

Scheme 104

Scheme 105

PICK-UP COIL RESISTANCE

PICK-UP COIL AIR GAP CHECK

1. Using a flat, non-magnetic feeler gauge, check air gap between signal rotor and pick-up coil projection.
2. Air gap should be .008-.016" (.20-.40 MM). If air gap is not within specification, replace distributor.

Scheme 106

Scheme 107

DASHPOT CONTROL SYSTEM TEST

1. Engine must be at normal operating temperature. Check idle speed and adjust, if necessary. Remove cap, filter and separator from dashpot.
2. Start engine. Maintain engine speed at specified testing RPM. See «DASHPOT TESTING RPM»(/toyota/corolla/vi-1987-1993/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. Plug the Vacuum Transmitting Valve (VTV) hole with your finger.
3. Release throttle. Dashpot should be extended and dashpot setting RPM should be as specified. See «DASHPOT TESTING RPM»(/toyota/corolla/vi-1987-1993/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. If idle speed is incorrect, adjust dashpot.
4. To check VTV operation, run engine at dashpot testing RPM for a few seconds. Plug the VTV hole with your finger. Release throttle. Uncover plugged hole. Engine should return to idle in about one second.
5. Install dashpot separator, filter and cap. Install filter with coarser surface facing outward.

DASHPOT TESTING RPM

Scheme 108

Scheme 109

SYSTEM TEST

1. Ensure modulator filter is clean and in good condition prior to performing test. Clean filter with compressed air as required. Disconnect vacuum hose from EGR valve.
2. Using a "T" connector, connect a vacuum gauge in EGR valve vacuum line. Check that engine starts and runs at idle. This ensures proper seating of EGR valve.
3. Different vacuum switching valves are used depending on model. The Bi-Metallic Vacuum Switching Valve (BVSV), Vacuum Switching Valve (VSV) and EGR modulator can be checked with engine coolant below minimum temperature and specified engine RPM in accordance with application. See «EGR SPECIFICATIONS»(/toyota/corolla/vi-1987-1993/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table.
4. Operate engine with engine coolant below minimum temperature and specified RPM. No vacuum reading should be obtained when operated with engine coolant below minimum temperature.
5. Operate engine at normal operating temperature and specified RPM. See «EGR SPECIFICATIONS»(/toyota/corolla/vi-1987-1993/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table for specified engine RPM. A low vacuum reading should be obtained.
6. At 5000 RPM, no vacuum should exist. Disconnect hose from the "R" port of EGR vacuum modulator. Using additional hose, connect "R" port directly to intake manifold. High vacuum reading should be obtained at specified engine RPM. See «EGR SPECIFICATIONS»(/toyota/corolla/vi-1987-1993/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. NOTE: Engine should misfire due to large amounts of exhaust gas being injected into intake manifold.
7. To check EGR valve, apply vacuum directly to EGR valve with engine idling. Engine should run rough. If system did not operate as described, each component should be tested.

EGR SPECIFICATIONS

Scheme 110

1. EGR vacuum modulator may be a 2-port or 3-port depending on application. On 2 port models, disconnect hoses from vacuum modulator. Plug one end of vacuum hose connection on EGR vacuum modulator.
2. Apply air pressure through remaining port. Air should pass freely through air filter side of modulator. On 3-port models, disconnect all hoses. Block ports "P" and "R". Apply air pressure to port "Q". Air should pass through the air filter side of modulator freely.
3. Operate engine at specified RPM. Refer to the «EGR VACUUM MODULATOR SPECIFICATIONS»(/toyota/corolla/vi-1987-1993/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. Repeat previous test procedure in steps 1) and 2). Strong resistance of airflow should be felt. Replace EGR vacuum modulator if resistance is not felt. Reconnect vacuum hoses to proper locations

EGR VACUUM MODULATOR SPECIFICATIONS

BI-METALLIC VACUUM SWITCHING VALVE (BVSV) (2WD 4A-GE)

1. Drain cooling system and remove BVSV. Using cool water, cool BVSV to below minimum temperature according to application. See the BVSV SPECIFICATIONS table.
2. Apply air through top port of valve. Air should NOT exhaust through bottom port. Heat BVSV valve to above maximum temperature according to application. See BVSV SPECIFICATIONS table. Apply air in top port. Air should exhaust through lower port. Replace assembly if defective. If BVSV does not function as described, replace valve.

BI-METALLIC VACUUM SWITCHING VALVE (BVSV) (4WD 4A-FE)

1. Drain cooling system and remove BVSV. Cool BVSV to minimum temperature according to application using cool water. Refer to the «BVSV SPECIFICATIONS»(/toyota/corolla/vi-1987-1993/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table.
2. Apply air to the lower port. Air should escape from air filter located on top of valve assembly. Heat BVSV valve to maximum temperature according to application. See «BVSV SPECIFICATIONS»(/toyota/corolla/vi-1987-1993/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table.
3. Apply air to the lower port. Air should exhaust from the upper port but not through the air filter. Replace assembly if defective.

BVSV SPECIFICATIONS

VACUUM SWITCHING VALVE (VSV) (2WD 4A-GE)

1. Unplug VSV connector. Connect battery to VSV terminals. Apply air pressure to port "E". Air should escape from port "F". Disconnect battery terminals.
2. Apply air pressure to port "E". Air should now escape from air filter. Using ohmmeter, check for continuity between terminals and VSV body. Replace unit if incorrect airflow or continuity exists.
3. Using ohmmeter, measure resistance between both terminals of valve assembly. Resistance should be 33-39 ohms at 68°F (20°C). Replace valve if resistance is not within specification.

Scheme 111

Scheme 112

Scheme 113

FUEL ODOR OR GAS LEAKS

Disconnected or cracked fuel vapor line or defective components in system. Check all lines and fittings. Check operation of system.

FUEL TANK OR EXPANSION TANK DEFORMED

Canister is clogged, vacuum relief filler cap is defective or hoses are clogged or kinked.

ROUGH ENGINE OPERATION

Check vacuum hose between vacuum solenoid valve (if equipped) and intake manifold for damage or loose connections. Check for malfunctions in all valves. Ensure all vacuum hoses are tight and in good condition.

BI-METALLIC VACUUM SWITCHING VALVE (BVSV)

1. Drain engine coolant. Remove BVSV. Connect hose to top port. Place valve in water that is less than 95°F (35°C). Blow air into hose. Ensure valve is closed.
2. Heat water to 129°F (54°C). Blow air into hose. Ensure valve is open. If valve is not open, replace valve. Apply liquid sealer to threads of valve before installing. Refill engine with coolant. If BVSV does not operate as described, replace valve.

CHARCOAL CANISTER

1. Check for clogged filter and/or stuck check valve by blowing low pressure compressed air into canister tank port. Check that air flows freely out of other canister ports.
2. Blow air into canister purge port. Check that air does not flow out of any other port.

MAINTENANCE

1. Inspect fuel tank, canister, vacuum relief filler cap, lines and hoses for damage, leaks, and deterioration every 60,000 miles or every 6 years. Replace gasket in vacuum relief filler cap.
2. To clean charcoal canister filter, remove hoses from canister and apply 43 psi (3 kg/cm 2 ) air pressure to fuel tank port. Hold other top ports closed. Ensure that no carbon comes out of bottom port of canister.

Scheme 114

Scheme 115

See also:
• AIRFLOW METER RESISTANCE SPECIFICATIONS
• PICK-UP COIL AIR GAP CHECK