EGR System - Gasoline Toyota Camry V10

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. 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.

EGR System (Celica). Scheme 35

VACUUM MODULATOR

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 "P" (single port on opposite side). Air should escape freely from filter.
2. Start engine and run at 2000 RPM on Camry and 3000 RPM on Celica. 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)

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, 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.

Scheme 36

1. Check and clean vacuum modulator filters with compressed air before proceeding with test.
2. 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 Celica. Check that vacuum gauge indicates zero at 2500 RPM on Camry and 3500 RPM on Celica. (Scheme 36): EGR System (Celica)
4. Check BVSV and EGR vacuum modulator with engine hot. Vacuum gauge should indicate low vacuum at 2500 RPM on Camry and 3500 RPM on Celica.
5. 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 and 3500 RPM on Celica. 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.