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EGR System - Gasoline Dodge Aries I

Testing & Diagnostics 3 illustrations ~1158 words

DESCRIPTION

The exhaust gas recirculation (EGR) system allows a predetermined amount of exhaust gas to recirculate to the intake manifold. This dilutes the incoming air/fuel mixture.

This diluting of the air/fuel mixture reduces peak flame temperatures during combustion. The reduced temperature reduces emissions of oxides of nitrogen (NOx).

OPERATION

Ported vacuum control provides signals for EGR operation on 1.6L and 2.2L 4-cylinder engines. The 2.6L 4-cylinder engine utilizes a carburetor vacuum controlled dual EGR control valve in addition to a mechanically-linked sub-EGR control valve.

1.6L & 2.2L 4-Cyl.

As the throttle blade opens, a slot type port in the carburetor throttle body is exposed to an increasing percentage of manifold vacuum. This port is connected through an external nipple directly to the EGR valve.

The flow rate is dependent on manifold vacuum, throttle position and exhaust gas back-pressure.

Ported Vacuum Control EGR System (1.6L & 2.2L 4-Cyl.). Scheme 13

Scheme 13: Ported Vacuum Control EGR System (1.6L & 2.2L 4-Cyl.)
Scheme 13: Ported Vacuum Control EGR System (1.6L & 2.2L 4-Cyl.)

2.6L 4-Cyl.

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

Sectional View of Dual EGR Control Valve. Scheme 14

Scheme 14: Sectional View of Dual EGR Control Valve
Scheme 14: Sectional View of Dual EGR Control Valve

The primary valve controls EGR flow at relatively small throttle opening angles. The secondary control valve allows recirculation of exhaust gas into the intake mixture at larger throttle opening angles.

Vacuum applied to the dual EGR control valve is controlled by a thermo valve. The sub-EGR valve is directly opened and closed with motion of the throttle valve through mechanical linkage.

Sectional View of Sub-EGR Control Valve. Scheme 15

Scheme 15: Sectional View of Sub-EGR Control Valve
Scheme 15: Sectional View of Sub-EGR Control Valve

Two thermo valves sense coolant temperature at the intake manifold and prevent operation of the dual EGR valve below the preset temperature of the thermo valve.

COOLANT CONTROL EGR VALVE (CCEGR)

The CCEGR valve is located in the thermostat housing on 4-cylinder engines. On V8 engines, the CCEGR valve is located in the intake manifold.

2.6L

  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, the secondary valve is operating properly. If no change, the EGR valve or thermo valve is not operating properly.
  5. Disconnect vacuum pump. Reconnect Green striped hose to carburetor. Disconnect Yellow striped hose. Connect vacuum pump to Yellow striped hose. Apply 6 in. Hg vacuum with hand pump.
  6. If engine idling speed becomes unstable, primary valve is operating properly. If no change, the EGR valve or thermo valve is not operating properly.

CCEGR VALVE

  1. Remove CCEGR valve from vehicle. Place it in an ice bath to bring temperature of coolant sensing portion to below 40°F (4°C).
  2. Attach a hand vacuum pump with gauge to the CCEGR nipple corresponding to the Yellow stripe hose on 4-cylinder engines.
  3. Apply vacuum of 10 in Hg. Observe gauge for 1 minute. There should be no more than 1 in. Hg drop in vacuum within this time. If so, replace CCEGR valve.

EGR VALVE

  1. Inspect valve for deposits with particular attention to the poppet and seat area. If deposits exceed a thin film, valve should be cleaned.
  2. Cleaning is aided by applying a liberal amount of manifold heat control solvent, or equivalent, to the poppet and seat area, allowing deposits to soften CAUTION: Extreme care should be taken when using solvent cleaners to prevent spilling of solvent on valve diaphragm.
  3. Use an external vacuum source to open poppet and then scrape deposit from this area. If wear of stem or other moving components is noted, valve should be replaced.

Note. Do not push valve stem manually, use an external vacuum source only.

TROUBLE SHOOTING

Note. All tests must be made with engine fully warm and running for at least 2 minutes.

EGR VALVE STEM DOES NOT MOVE ON SYSTEM TEST

  1. Check for cracked, leaking, disconnected or plugged vacuum. Replace any defective hoses.
  2. Connect an external vacuum source to EGR valve diaphragm. Apply at least 10 in. Hg to valve. If no valve movement occurs, Diaphragm is ruptured or stem is frozen. Replace EGR valve.
  3. If valve opens 1/8" (3 mm), pinch off supply hose to check for diaphragm leakage. Valve should remain open for at least 30 seconds. If leakage occurs, replace EGR valve.

EGR VALVE STEM DOES NOT MOVE ON SYSTEM TEST, BUT OPERATES NORMALLY ON EXTERNAL VACUUM SOURCE

  1. Disconnect CCEGR valve and by-pass valve with a short length of 3/16" tubing. If normal movement of EGR valve is restored, replace CCEGR valve.
  2. On venturi vacuum type systems, disconnect Orange and Blue (or unstriped) hoses at time delay solenoid valve and by-pass valve with at short piece of tubing.
  3. If normal EGR valve stem movement is restored, reconnect hoses to valve and disconnect electrical plug from solenoid. If EGR valve stem does not move, solenoid should be replaced.
  4. If solenoid does move, timer should be further tested as previously described.
  5. If plugged passages are suspected with the ported vacuum type system, carburetor should be removed and slots inspected and cleaned as necessary. Recheck for normal EGR operation.
  6. If plugged passages are suspected with the venturi vacuum system, carburetor cleaner should be used to clean deposits from venturi passage. Use light air pressure to verify that passage is clean.
  7. To check for defective vacuum amplifier (venturi vacuum systems), remove venturi vacuum signal hose from carburetor. With engine at idle, apply approximately 2 in. Hg vacuum to the signal hose.
  8. Engine speed should drop at least 150 RPM and EGR valve stem should move 1/8" (3 mm) or more. If not, replace vacuum amplifier.

ENGINE WILL NOT IDLE, DIES ON RETURN TO IDLE OR ROUGH IDLE (EGR VALVE OPEN AT IDLE)

  1. On venturi vacuum systems, disconnect and plug vacuum hose from EGR valve. If idle is unsatisfactory, replace EGR valve.
  2. If idle is okay, reconnect hose to valve and disconnect hose from carburetor. If idle is okay, clean venturi tap. If idle not okay, replace vacuum amplifier.
  3. On ported vacuum systems, disconnect and plug vacuum hose from EGR valve. If idle is not okay, replace EGR valve.
  4. If idle is still rough, install vacuum gauge on ported signal tap. If more than 1" of vacuum is present, check idle setting. If vacuum is okay, check linkage and carburetor for binding.

ENGINE WILL NOT IDLE, DIES ON RETURN TO IDLE OR ROUGH IDLE (EGR VALVE CLOSED AT IDLE)

If removal of vacuum hose from EGR valve does not correct rough idle, remove EGR valve and inspect to ensure that poppet is seated. Clean deposits from valve or replace EGR valve if necessary.

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