Toyota Service Blog

Exhaust Gas Recirculation Egr System

EGR Port

Vacuum

Modulator

Temp. Sensor

EGR Valve

EGR Port

Vacuum

Modulator

EGR Valve

Temp. Sensor icwo

EGR Port

R Port

Vacuum

Modulator

EGR Valve

Pressure Chamber

Cooler

Cooler

EGR Port

R Port

Vacuum

Modulator

EGR Valve

Pressure Chamber ccotn

EGR Port

Port

EGR Port

Port

Vacuum

Modutator

EGR Valve

Pressure Chamber

EGR Port

R Port

Vacuum

Modutator

EGR Valve

Pressure Chamber

EGR Port

R Port

Vacuum

Modulator

EGR Valve

Pressure Chamber

Vacuum

Modulator

EGR Valve

Pressure Chamber icotn

To reduce NOx emission, part of the exhaust gases are recirculated through the EGR valve to the intake manifold to lower the maximum combustion temperature.

Coolant Temp.	VSV	Throttle Valve Opening Angle	Pressure In the EGR Valve Pressure Chamber		EGR Vacuum Modulator	EGR Valve	Exhaust Gas
Below 570c (135°F) 0PEN		—	—		—	CLOSED	Not recirculated
Above 63°C C145°F|	CLOSE	Positioned below EGR port	—		—	CLOSED	Not recirculated
		Positioned be tween EGR port and R port	<11 LOW	•Pressure con-stantly alternating between low and high	OPENS passage to atmosphere	CLOSED	Not recirculated
			(2) HIGH		CLOSES passage to atmosphere	OPEN	Recirculated
		Positioned above R port	(3) HIGH	• •	CLOSES passage to atmosphere	OPEN	Recirculated (increase)

Remarks: • Pressure increase Modulator closes EGR valve opens Pressure drops

••When the throttle valve is positioned above the R port, the EGR vacuum modulator will close the atmosphere passage and open the EGR valve to increase the EGR gas. even if the exhaust pressure is insufficiently low.

Remarks: • Pressure increase Modulator closes EGR valve opens Pressure drops

••When the throttle valve is positioned above the R port, the EGR vacuum modulator will close the atmosphere passage and open the EGR valve to increase the EGR gas. even if the exhaust pressure is insufficiently low.

INSPECTION OF EGR VALVE

1. CHECK AND CLEAN FILTER IN EOR VACUUM MODULATOR

(a) Check the filter for contamination or damage. <b) Using compressed air, clean the filter.

Vacuum Gauge

Vacuum Gauge

ICC9J4

2. PREPARATION

Disconnect the vacuum hose from the EGR valve and, using a three way union, connect a vacuum gauge to it.

COLD

COLD

fCOD? f CCI W

3. CHECK SEATING OF EGR VALVE

Start the engine and check that the engine starts and runs at idle.

4. CHECK VSV WITH COLD ENGINE

(a) The coolant temperature should be below 57°C (135°F).

(b) Check that the vacuum gauge indicates zero at 2,500 rpm.

5. CHECK VSV AND EGR VACUUM MODULATOR WITH WARM ENGINE

(b) Check that the vacuum gauge indicates about 70 mm Hg (2.76 in.Hg, 9.3 kPa) at 2r500 rpm.

(c) Check that the vacuum gauge indicates zero at idle.

Tachomcter Vacuum G¿uge

(d) Disconnect the vacuum hose from R port of the EGR vacuum modulator and connect R port directly to the intake manifold with another hose.

(e) Check that the vacuum gauge indicates high vacuum at 2,500 rpm.

NOTE: As a large amount of EGR gas enters, the engine will misfire.

(f) Disconnect the vacuum gauge and reconnect the vacuum hoses to the proper locations.

2,500 rpm Low Vacuum

2,500 rpm Low Vacuum

Tachomcter Vacuum G¿uge

6. CHECK EGR VALVE

(a) Apply vacuum directly to the EGR valve with the engine idling.

(b) Check that the engine runs rough or dies.

(c) Reconnect the vacuum hoses to the proper location.

IF NO PROBLEM IS FOUND WITH THIS INSPECTION, THE SYSTEM IS OKAY; OTHERWISE INSPECT EACH PART

INSPECTION OF EGR VACUUM MODULATOR

CHECK EGR VACUUM MODULATOR OPERATION

(a) Disconnect the vacuum hoses from ports P, Q and R of the EGR vacuum modulator.

(b) Block ports P and R with your finger.

(c) Blow air into port Q. Check that the air passes through to the air filter side freely.

(d) Start the engine and maintain engine speed at 2,500 rpm.

(e) Repeat the above test. Check that there is a strong resistance to air flow.

(f) Disconnect the vacuum hoses to the proper locations. If a problem is found, replace the EGR vacuum modulator.

INSPECTION OF VSV

1. CHECK VACUUM CIRCUIT CONTINUITY IN THE VSV BY BLOWING AIR INTO PIPE

(a) Connect the VSV terminals to the battery terminals as illustrated.

(b) Blow air into a pipe and check that the VSV is open.

(c) Disconnect the battery.

(d) Blow air into a pipe and check that the VSV is closed. If a problem is found, replace the VSV.

2. CHECK FOR SHORT CIRCUIT

Using an ohmmeter, check that there is no continuity between the terminals and the VSV body.

If there is continuity, replace the VSV.

3. CHECK FOR OPEN CIRCUIT

Using an ohmmeter, measure the resistance between the terminals.

If the resistance is not within specification, replace the VSV.

INSPECTION OF EGR VALVE

1. REMOVE EGR VALVE

Check the valve for sticking and heavy carbon deposits. If a problem is found, replace it.

2. INSTALL EGR VALVE WITH NEW GASKET

INSPECTION OF WATER TEMP. SENSOR (See page FI-73)