EGR System Dodge Grand Caravan I

DESCRIPTION

Exhaust Gas Recirculation (EGR) allows a predetermined amount of hot exhaust gas to recirculate in intake manifold. This dilutes incoming air/fuel mixture.

This diluting of air/fuel mixture reduces peak flame temperature during combustion, thereby reducing emissions of oxides of nitrogen (NOx).

OPERATION

Ported vacuum control provides signals for EGR operation on 2.2L engine. The 2.6L engine utilizes carburetor vacuum controlled dual EGR control valve in addition to mechanically-linked sub-EGR control valve.

2.2L

As throttle blade opens, slot-type port in carburetor throttle body is exposed to an increasing percentage of manifold vacuum. This port is connected through an external nipple directly to EGR. Flow rate is dependent on manifold vacuum, throttle position and exhaust gas back-pressure.

Scheme 51

2.6L

Dual EGR system has primary and secondary valves which respond to different carburetor vacuums in response to throttle openings. EGR operation is suspended at idle and wide open throttle.

Primary valve controls EGR flow at relatively small throttle opening angles. Secondary control valve allows recirculation of exhaust gas into intake mixture at larger throttle opening angles.

Vacuum applied to dual EGR control valve is controlled by thermo valve. Sub-EGR valve is directly opened and closed with motion of throttle valve through mechanical linkage. Two thermo valves sense coolant temperature at intake manifold and prevent operation of dual EGR valve below preset temperature of thermo valve.

Scheme 52

Scheme 53

Scheme 54

COOLANT VACUUM SWITCH COLD CLOSED VALVE (CVSCC)

CVSCC valve is used with EGR system to delay EGR operation until engine warm-up is achieved. Valve location and opening temperature varies according to vehicle model and engine type.

On models with CVSCC valve in radiator tank, opening temperature is 59°F (15°C). On models with valve in thermostat housing, opening temperature is 108-125°F (42-52°C).

Scheme 55

COOLANT TEMPERATURE SENSOR OR CHARGE TEMPERATURE SENSOR

This sensor is located in a water passage or intake manifold runner. By monitoring engine temperature it signals the computer when to operate the air switching in the EGR and Spark Advance systems.

EGR MAINTENANCE REMINDER SYSTEM

The purpose of this system is a reminder that the emission maintenance must be performed as soon as possible. It is not intended to indicate a warning.

Heavy Duty Vehicles

Instrument panel light will come on when the first 12,000 miles has been reached, and every subsequent 12,000 miles thereafter.

Light Duty Vehicles

Instrument panel light will come on when the first 52,224 miles has been reached, and every subsequent 52,224 miles thereafter.

Reset Procedure

After the necessary maintenance has been completed reset the system module as follows.

1. Slide module off its bracket (located behind instrument panel). Leave vehicle battery connected. Leave module wires connected.
2. Remove module battery cover and remove 9-volt battery. Reset module by inserting a small screwdriver blade or rod into small hole in module case.
3. Replace 9-volt battery with a new one. Slide module back onto its bracket.

1. Place transmission in Neutral (man. trans.) or "P" (auto. trans.). Start engine and warm to normal operating temperature by idling engine.
2. Abruptly open throttle to approximately 2000-3000 RPM. Visible movement of EGR valve stem should be noted. Repeat several times (if necessary).
3. Attach hand vacuum pump to EGR valve with engine at idle. Apply at least 5 in. Hg of vacuum and engine should run rough or stall.
4. Attach vacuum gauge to EGR hose and open throttle quickly several times. Fluctuation of several in. Hg should be noted.

1. Check vacuum hose condition, routing and installation. Start cold engine and run at idle. Increase engine speed to 2500 RPM. Secondary EGR valve should not operate. If secondary EGR valve operates, replace thermo valve.
2. Warm engine to at least 150°F (66°C). Accelerate engine to 2500 RPM. Secondary EGR valve should operate. If it does not, inspect EGR valve or thermo valve and replace as necessary.
3. Disconnect Green striped hose from nipple on carburetor. Connect vacuum pump to hose. Pull sub-EGR valve by hand and apply 6 in. Hg vacuum.
4. If engine idling speed becomes unstable, secondary valve is operating properly. If no change, EGR valve or thermo valve is not operating properly.
5. Disconnect vacuum pump. Reconnect Green striped hose to carburetor. Disconnect Yellow striped hose. Apply 6 in. Hg vacuum with hand pump.
6. If engine idling speed becomes unstable, primary valve is operating properly. If idle speed does not change, replace EGR valve or thermo valve.

2.2L & 2.6L

1. Remove CVSCC valve from vehicle. Place it in ice bath to bring temperature of coolant sensing portion to below 40°F (4°C).
2. Attach hand vacuum pump with gauge to CVSCC lower nipple and apply 10 in. Hg. of vacuum. Observe gauge for one minute. There should be no more than 1 in. Hg drop in vacuum within this time. If so, replace CVSCC valve.

EGR DELAY SYSTEM TEST

1. With Delay System (if equipped), stop engine, and then restart. Immediately open throttle to approximately 1000 RPM, and watch EGR valve stem for movement. (Scheme 56)
2. If it moves during first 30 seconds after starting, EGR time delay system is defective.
3. Check hose connections to time delay solenoid valve. If okay, detach electrical plug from solenoid valve. Energize valve by grounding either terminal and connecting other terminal to positive battery post.
4. If EGR valve stem moves on this test, solenoid valve is defective and must be replaced. If EGR valve stem did not move, EGR timer control should be replaced. If this does not correct the problem, check wiring for proper connections.

EGR VALVE STEM DOES NOT MOVE ON SYSTEM TEST

1. Check for correct hose connections. Leak check to confirm all hoses are in good condition.
2. Check EGR valve for ruptured diaphragm or frozen valve stem. Connect external vacuum source of 10 in. Hg or greater to valve diaphragm. If no valve movement occurs, replace valve.
3. If valve opens 1/8" (3 mm), pinch off supply hose to check for diaphragm leakage. Valve should remain open 30 seconds or longer. If leakage occurs, replace valve.

EGR VALVE STEM DOES NOT MOVE ON TEST; OPERATES NORMALLY WITH EXTERNAL VACUUM APPLIED

1. Follow this procedure to check system for defective CVSCC valve or CTS: On CVSCC systems, by-pass CVSCC valve and connect vacuum amplifier directly to EGR valve. If EGR valve operates normally, replace CVSCC valve. On CTS systems, by-pass EGR solenoid and connect vacuum amplifier directly to EGR valve. If EGR valve operates normally, reconnect EGR solenoid hoses, and remove wire from timer terminal of CTS. If EGR valve operates within 90 seconds, replace CTS.
2. In Venturi Vacuum Control System, remove venturi vacuum hose from carburetor nipple. With engine at idle, apply 2 in. Hg vacuum to hose. Engine speed should drop 150 RPM or more, and EGR valve stem should move 1/8" (3 mm) or more. If this does not occur, replace vacuum control valve.
3. If vacuum control amplifier operated normally in previous test, plugged vacuum tap to carburetor is indicated. Use carburetor solvent to remove deposits from passage, and clear with light air pressure.

Note. Do not use drills or wires to clean carburetor control passages for either control system. Calibration of precision orifices could be altered, resulting in unsatisfactory vehicle operation.

ROUGH IDLE, SLOW IDLE, OR STALL ON RETURN TO IDLE

1. Disconnect hose from EGR valve and plug hose. Recheck idle. If satisfactory, replace vacuum control amplifier.
2. If vacuum hose removal does not correct problem, remove EGR valve and inspect to ensure poppet is seated. Clean poppet seat, or replace if poppet does not seat correctly.

POOR COLD DRIVEABILITY, ROUGH IDLE OR STALLS ON RETURN TO IDLE

CVSCC valve or EGR control valve could be leaking. Check by performing leak test, and replace valves as necessary.

WEAK PERFORMANCE AT WIDE OPEN THROTTLE

Disconnect hose from EGR valve and plug hose. Road test vehicle. If performance is restored, replace vacuum control amplifier.

Scheme 56