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
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 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
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)
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