Chrysler Colt/Vista 1990-1993 Repair Information

Exhaust Gas Recirculation System (EGR)

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See Figures 1, 2, 3 and 4



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Fig. Fig. 1: EGR system - 1990-92 Colt hatchback and sedan w/1.5L - California only



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Fig. Fig. 2: EGR system - 2.0L engine



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Fig. Fig. 3: EGR system - 1992-93 Vista w/1.8L engine



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Fig. Fig. 4: EGR system - 2.4L engine

OPERATION.



Exhaust Gas Recirculation is used to reduce peak flame temperatures in the combustion chamber. A small amount of exhaust gas is diverted from the exhaust manifold and re-entered into the intake manifold, where it mixes with the air/fuel charge and enters the cylinder to be burned. Cooler combustion reduces the formation of Nitrogen Oxide (NO 2 ) emissions

The system consists of the EGR valve, controlling the flow of exhaust gas and various vacuum and/or electric controls to keep the EGR from working at the incorrect time.

No EGR is required when the engine is cold due to lower flame temperatures in the engine. EGR under these conditions would produce rough running so EGR function is cut off either by a thermo valve or by the fuel injection computer (which is monitoring coolant temperature.) Additionally, EGR flow is cut off at warm idle to eliminate any roughness or stumble on initial acceleration.

Cooler combustion temperatures also result in slightly reduced power output. This isn't felt during normal, part-throttle driving and the emission benefits outweigh the slight loss. However, in a wide-open throttle situation a power reduction is not desirable; full power could be the margin of success in a passing or accident avoidance situation. For this reason, EGR function is eliminated when the engine goes on wide-open throttle. Normally, the vacuum to the EGR valve can overcome the spring tension within the valve and hold it open. When the throttle opens fully, vacuum to the EGR is reduced and the spring closes the valve.

A common symptom of EGR malfunction is light engine ping at part throttle, particularly noticeable under load such as going uphill or carrying several passengers. An EGR valve which fails to close properly can also cause a rough or uneven idle. If the engine is correctly tuned and other common causes (vacuum leaks, bad plug wires, etc.) are eliminated, EGR function should considered as a potential cause when troubleshooting a rough idle.

Since the majority of EGR components do not require routine maintenance and should not clog or corrode if unleaded gas is used, you should check all other reasonable causes of a problem before checking this system.

TESTING



System Test
ALL EXCEPT CALIFORNIA
  1. Allow the engine to cool overnight. Since the EGR system works differently for warm and cold engines, a completely cold engine is required for testing.
  2.  
  3. Disconnect the vacuum hose with the green stripe from the throttle body. Attach the end of the hose to vacuum pump.
  4.  
  5. Plug the port from which the hose was removed. Start the engine and attempt to draw a vacuum with the hand pump. The system should NOT hold vacuum with the engine cold and running at idle.
  6.  
  7. Allow the engine to run at idle until an engine temperature of 176°F (80°C), or higher, is reached. Draw a vacuum of 1.6 in.Hg and listen to the engine idle. There should be no change in the engine. Increase the vacuum to 7.9 in.Hg. As the correct vacuum is reached, the idle should roughen, become uneven, or possibly stall as the EGR valve opens and admits exhaust gas. The system should hold vacuum while the valve is open.
  8.  

CALIFORNIA CARS
  1. Allow the engine to cool overnight. Since the EGR system works differently for warm and cold engines, a completely cold engine is required for testing.
  2.  
  3. Disconnect the vacuum hose with the green stripe from the EGR valve. Using a vacuum tee and a short length of vacuum hose, attach a hand-held vacuum pump to the system.
  4.  
  5. Start the engine, quickly open the throttle and attempt to draw a vacuum with the hand pump. The system should NOT hold vacuum with the engine cold and running at idle.
  6.  
  7. Allow the engine to run at idle until it reaches at least 158°F (70°C). Open the throttle quickly. A momentary vacuum reading of 3.9 in.Hg will be noted.
  8.  

EGR Valve
  1. Disconnect the vacuum line from the EGR valve.
  2.  
  3. Connect a hand-held vacuum pump directly to the valve nipple.
  4.  
  5. Apply 20 in.Hg vacuum. Vacuum should be held.
  6.  

Control Solenoid Valve
  1. Disconnect the vacuum hose (yellow stripe/green stripe) from the control solenoid valve.
  2.  
  3. Disconnect the wiring harness from the valve.
  4.  
  5. Connect a hand-held vacuum pump to the valve's nipple.
  6.  
  7. Apply vacuum and check valve operation. The vacuum should not be held.
  8.  
  9. Apply battery voltage to the valve. Vacuum should be held.
  10.  
  11. Check resistance across the valve's terminals with an ohmmeter. Resistance should be 36-44-.
  12.  

Temperature Sensor
  1. Remove the sensor. See Section 3.
  2.  
  3. Place the sensor in a pot of water along with a thermometer, and connect an ohmmeter across the sensor's harness connector terminals.
  4.  
  5. Raise the water temperature to 122 °F (50°C). Resistance should be 60-83-.
  6.  
  7. Raise the water temperature to boiling. Resistance should be 11-14-.
  8.  

Thermo Valve
  1. Disconnect the two vacuum hoses on the thermo valve.
  2.  
  3. With the engine off and cold, connect a hand-held vacuum pump to the upper port.
  4.  
  5. Apply vacuum and confirm that the valve does NOT hold vacuum.
  6.  
  7. Start the engine and allow it to warm up to at least 176°F (80°C). When the coolant has reached normal operating temperature, disconnect the appropriate hose as before and repeat the test; the valve should hold vacuum and not leak.
  8.  

REMOVAL & INSTALLATION



EGR Valve
  1. Label and disconnect the hoses from the valve. Carefully loosen and remove the retaining bolts, remembering that they are probably heat-seized and rusty. Use penetrating oil freely.
  2.  
  3. Remove the valve and clean the gasket remains from both mating surfaces.
  4.  
  5. Inspect the valve for any sign of carbon deposits or other cause of binding or sticking. The valve must close and seal properly; the pintle area may be cleaned with solvent to remove soot and carbon.
  6.  
  7. Install the valve with a new gasket. Tighten the bolts to 10 ft. lbs. for the 2.4L, 1991-93 1.5L and 1992-93 1.8L; 13 ft. lbs. for the 1990 1.5L and 1990 1.8L; 16 ft. lbs. for the 1.6L and 2.0L.
  8.  
  9. Connect the hoses.
  10.  

Thermo Valve

If it becomes necessary to replace the thermovalve, do so only on a cold engine. Fit the wrench only onto the faceted base of the valve, never on the plastic parts. When installing the new unit, apply sealer such as 3M No. 4171® or equivalent to the threads and tighten the new unit to 22 ft.lbs. (30 Nm)

 
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