EGR System - Gasoline Toyota 4Runner I

DESCRIPTION

The exhaust gas recirculation (EGR) system is used to reduce the formation of NOx emissions by reducing combustion temperature. This is accomplished by recycling metered amounts of exhaust gas back into the intake system.

Each system has a vacuum-operated EGR valve and a vacuum modulator. California carbureted Pickup and 4Runner do not use a vacuum modulator. All models use temperature sensing devices for controlling EGR operation.

The device used could be a vacuum switching valve (VSV), a bi-metallic vacuum switching valve (BVSV), a thermostatic vacuum switching valve (TVSV), or a combination of these valves. A check valve, EGR cooler and computer can also be used on some models.

OPERATION

When engine is not at operating temperature, no exhaust gas recirculation will occur since the switching valve is closed. Once engine temperature increases, the switching valve opens and exhaust gas recirculation is then controlled by other components of the system.

Vacuum modulator reacts to relieve exhaust backpressure, and to balance atmospheric pressure and vacuum to allow or stop EGR. The EGR cooler, used on Cressida, Land Cruiser and Supra, assists in reducing exhaust gas temperature before it is cycled into combustion chamber. This helps further reduce high temperatures that cause NOx formation.

EGR System (Camry). Scheme 17

VACUUM MODULATOR (FWD COROLLA)

1. Disconnect vacuum hoses from ports "P", "Q" and "R" of vacuum modulator. Plug ports "Q" and "R" (2 ports on same side) and blow through port "P" (single port on opposite side). Air should escape freely from filter.
2. Start engine and run at 2000 RPM. Repeat blowing test. There should be strong resistance to air flow through modulator. If not, replace modulator. Reconnect vacuum hoses to proper locations.

VACUUM MODULATOR (CARBURETED RWD COROLLA & TERCEL)

1. Disconnect vacuum hoses from both ports of vacuum modulator. Plug port nearest EGR valve and blow air into port farthest from EGR valve. Air should escape freely through air filter of modulator.
2. Start engine and maintain engine speed at 3000 RPM. Repeat blow test. There should be strong resistance to air flow. If not, replace vacuum modulator. Reconnect vacuum hoses to proper locations.

VACUUM MODULATOR (ALL OTHER MODELS)

1. Disconnect vacuum hoses from ports "P", "Q" and "R" of vacuum modulator. Plug ports "P" and "R" (2 ports on same side) and blow through port "Q" (single port on opposite side). Air should escape freely from filter.
2. Start engine and run at 3000 RPM on Celica, Pickup and 4Runner, or 2500 RPM on all other models. Repeat blowing test. There should be strong resistance to air flow through modulator. If not, replace modulator. Reconnect vacuum hoses to proper locations.

BI-METALLIC VACUUM SWITCHING VALVE (BVSV) - CAMRY, CELICA, PICKUP & 4RUNNER

1. Drain coolant and remove BVSV valve. Place sensing portion in cool water, but do not allow water into valve.
2. Cool BVSV to below 113°F (45°C) on Camry, and below 86°F (30°C) on all others. Blow air into bottom port and check that air escapes through filter.
3. Heat BVSV to above 111°F (44°C) on Celica, Pickup and 4Runner, and above 150°F (66°C) on Camry. Blow air into bottom port and check that air escapes through top port.
4. Apply liquid sealer to threads of BVSV and reinstall. Fill radiator with coolant. If problem is found, replace BVSV.

BI-METALLIC VACUUM SWITCHING VALVE (BVSV) - FUEL INJECTED COROLLA, LAND CRUISER, MR2 & VAN

1. Drain coolant and remove BVSV valve. Place sensing portion in cool water, but do not allow water into valve.
2. Cool BVSV to below 86°F (30°C) on Land Cruiser, 95°F (35°C) on Corolla and MR2, and below 104°F (40°C) on Van. Blow air into top port and check that air does not escape through bottom port.
3. Heat BVSV to above 111°F (44°C) on Land Cruiser and above 129°F (54°C) on all others. Blow air into top port and check that air escapes through bottom port.
4. Apply liquid sealer to threads of BVSV and reinstall. Fill radiator with coolant. If problem is found, replace BVSV.

THERMOSTATIC VACUUM SWITCHING VALVE (TVSV) - CARBURETED COROLLA & TERCEL

1. Drain coolant from radiator and remove TVSV. Place threaded end of valve in container of ice water with thermometer. With temperature below 45°F (7°C), check that air flows from port "J" to ports "L" and "M" and from port "K" to port "N". (Scheme 18)
2. Heat water to 63-122°F (17-50°C). Check that air flows from port "K" to ports "N" and "L" and from port "J" to port "M".
3. Continue heating water to above 154°F (68°C). Check that air flows from port "K" to ports "M" and "L" and does not flow from port "J" to any other port.
4. Apply liquid sealer to threads of TVSV and reinstall. Fill radiator with coolant. If problem is found, replace TVSV.

Testing Thermostatic Vacuum Switching Valve (TVSV). Scheme 18

Scheme 19

1. Connect battery voltage to VSV terminals. (Scheme 19) Blow air into port "E" (nearest valve) and check that air comes out port "F" (farthest from valve). Disconnect battery and repeat test. Air should not come out port "F" on Cressida and Supra, but should come out front port ("G") on Land Cruiser. (Scheme 19): Vacuum Switching Valve (VSV) Test Connections
2. Using an ohmmeter, check that there is no continuity between positive terminal and body of VSV. Resistance between terminals should measure 38-43 ohms at 68°F (20°C). Replace valve if it does not meet specifications.

CHECK VALVE (COROLLA & TERCEL)

Disconnect vacuum hoses and remove valve. Blow through valve. Air should flow from Orange side to Black side, but not from Black to Orange. Replace valve if it does not perform as outlined.

Scheme 20

1. Check and clean vacuum modulator filters with compressed air before proceeding with test. On California carbureted Pickup and 4Runner, disconnect and plug vacuum hose at distributor main diaphragm.
2. On all models, disconnect vacuum hose from EGR valve and, using a "T" connector, connect a vacuum gauge. Check that engine starts and runs at idle.
3. Check BVSV with coolant temperature below 113°F (45°C) on Camry and 86°F (30°C) on all others. Check that vacuum gauge indicates zero at 2500 RPM on Camry, 3000 RPM on carbureted Pickup and 4Runner, and 3500 RPM on Celica and fuel injected Pickup and 4Runner. (Scheme 20): EGR System (Celica and Fuel Injected Pickup & 4Runner)
4. Check BVSV and EGR vacuum modulator with engine hot. Vacuum gauge should indicate low vacuum at 2500 RPM on Camry, 3000 RPM on Federal carbureted Pickup and 4Runner, and 3500 RPM on Celica and fuel injected Pickup and 4Runner. High vacuum reading should be observed at 3000 RPM on California carbureted Pickup and 4Runner.
5. On all except California carbureted Pickup and 4Runner, disconnect vacuum hose from port "R" of EGR vacuum modulator and connect port directly to intake manifold vacuum.
6. Vacuum gauge should indicate high vacuum at 2500 RPM on Camry, 3000 RPM on Federal carbureted Pickup and 4Runner, and 3500 RPM on Celica and fuel injected Pickup and 4Runner. Disconnect vacuum gauge and reconnect hoses to proper locations. NOTE: This will cause slight engine misfire due to a large amount of exhaust gas being injected into intake manifold.
7. On all models, with engine idling, apply vacuum directly to EGR valve. Engine should run rough or die. Remove vacuum and reconnect vacuum hoses to proper locations. Engine should run smooth. If no problem is found with this inspection, system is okay.

EGR System (Federal Carbureted Pickup & 4Runner). Scheme 21

Scheme 22

Scheme 23

Scheme 24

Scheme 25

1. Check and clean vacuum modulator filters with compressed air before proceeding with test. Using a 3-way connector, connect a vacuum gauge to the hose between EGR valve and EGR vacuum modulator.
2. Check seating of EGR valve by starting engine. Engine should start and run at idle.
3. Check BVSV with coolant temperature below 86°F (30°C) on Land Cruiser; 95°F (35°C) on Corolla and MR2; and 104°F (40°C) on Van. Vacuum gauge should indicate low vacuum at 2500 RPM on Land Cruiser and 3500 RPM on all others. On Corolla EFI, vacuum should be zero. (Scheme 22): EGR System (California Carbureted Pickup & 4Runner) (Scheme 23): EGR System (Fuel Injected Corolla & MR2) (Scheme 24): EGR System (Land Cruiser)
4. Warm engine to normal operating temperature. Vacuum gauge should indicate low vacuum at 2500 RPM on Land Cruiser and 3500 RPM for all others. On Corolla and MR2, gauge should read zero at 5000 RPM.
5. Disconnect vacuum hose from port "R" of EGR vacuum modulator and connect port directly to intake manifold vacuum. Vacuum gauge should indicate high vacuum at 2500 RPM on Land Cruiser and 3500 RPM for all others. Disconnect vacuum gauge and reconnect hoses to proper locations. NOTE: This will cause slight engine misfire due to a large amount of exhaust gas being injected into intake manifold.
6. With engine idling, apply vacuum directly to EGR valve. Engine should run rough or die. Remove vacuum and reconnect vacuum hoses to proper locations. Engine should run smooth. If no problem is found with this inspection, system is okay. (Scheme 25): EGR System (Van)
7. On Land Cruiser, check computer control of vacuum switching valve (VSV). Disconnect vacuum hoses from ports "E" and "F" of VSV. (Scheme 26) With engine idling, blow into port "F". The valve should close and not allow air to escape through port "E".
8. Increase engine speed to above 1500 RPM. Again blow into port and note that valve should open to allow air to escape from port "E". If no problem is found with this inspection, system is okay.

Checking Computer Control of VSV (Land Cruiser). Scheme 26

Scheme 27

1. Check and clean vacuum modulator filters with compressed air before proceeding with test. Disconnect vacuum hose from EGR valve and, using a "T" connector, connect a vacuum gauge. Check that engine starts and runs at idle.
2. Check TVSV with coolant temperature below 122°F (50°C). Check that vacuum gauge indicates zero at 2000 RPM on FWD Corolla and 3000 RPM on RWD Corolla and Tercel. (Scheme 27): EGR System (Carbureted RWD Corolla & Tercel)
3. Check TVSV and EGR vacuum modulator with engine hot. Vacuum gauge should indicate low vacuum at 2000 RPM on FWD Corolla and 3000 RPM on RWD Corolla and Tercel.
4. On FWD Corolla, disconnect vacuum hose from port "R" of EGR vacuum modulator and connect port directly to intake manifold vacuum. Vacuum gauge should indicate high vacuum at 2000 RPM. Disconnect vacuum gauge and reconnect hoses to proper locations. NOTE: This will cause slight engine misfire due to a large amount of exhaust gas being injected into intake manifold.
5. On all models, with engine idling, apply vacuum directly to EGR valve. Engine should run rough or die. Remove vacuum and reconnect vacuum hoses to proper locations. Engine should run smooth. If no problem is found with this inspection, system is okay.

Scheme 28

Scheme 29

1. Check and clean vacuum modulator filters with compressed air before proceeding with test. Disconnect vacuum hose from EGR valve and, using a "T" connector, connect a vacuum gauge. Check that engine starts and runs at idle.
2. Check VSV with coolant temperature below 135°F (57°C). Check that vacuum gauge indicates zero at 2500 RPM. (Scheme 28): EGR System (FWD Corolla) (Scheme 29): EGR System (Cressida & Supra)
3. Check VSV and EGR vacuum modulator with engine hot. Vacuum gauge should indicate about 3 in. Hg at 2500 RPM and zero at idle.
4. Disconnect vacuum hose from port "R" of EGR vacuum modulator and connect port directly to intake manifold vacuum. Vacuum gauge should indicate high vacuum at 2500 RPM. Disconnect vacuum gauge and reconnect hoses to proper locations. NOTE: This will cause slight engine misfire due to a large amount of exhaust gas being injected into intake manifold.
5. With engine idling, apply vacuum directly to EGR valve. Engine should run rough or die. Remove vacuum gauge and reconnect vacuum hoses to proper locations. Engine should run smooth. If no problem is found with this inspection, system is okay.