Exhaust Gas Recirculation (EGR) system – description and component replacement
Description
1. Oxides of nitrogen, or simply NOx, are compounds that are formed in the engine when the oxygen and nitrogen in the incoming air mix together. When NOx is emitted from the tailpipe, it mixes with other compounds and sunlight to form ozone and smog. The EGR system reduces NOx by recirculating exhaust gases from the exhaust manifold through the EGR valve and intake mani¬fold, then back to the combustion chambers, where it mixes with the incoming air/fuel mix¬ture. These recirculated exhaust gases dilute the incoming air/fuel mixture, which cools the combustion chambers, thereby reducing NOx emissions.
2. The EGR system consists of the Power-train Control Module (PCM), the EGR valve and various information sensors that the PCM uses to determine when to open the EGR Description1 Oxides of nitrogen, or simply NOx, arecompounds that are formed in the engine when the oxygen and nitrogen in the incoming air mix together. When NOx is emitted from the tailpipe, it mixes with other compounds and sunlight to form ozone and smog. The EGR system reduces NOx by recirculating exhaust gases from the exhaust manifold through the EGR valve and intake mani¬fold, then back to the combustion chambers, where it mixes with the incoming air/fuel mix¬ture. These recirculated exhaust gases dilute the incoming air/fuel mixture, which cools the combustion chambers, thereby reducing NOx emissions.2 The EGR system consists of the Power-train Control Module (PCM), the EGR valve and various information sensors that the PCM uses to determine when to open the EGR valve. When the PCM chooses, a solenoid inside the EGR valve is energized. This lifts the pintle valve off its seat. The exhaust gas then flows from the exhaust manifold port to the intake manifold.
3. Once activated by the PCM, the EGR valve uses a feedback circuit to control the position of the pintle valve. This enables the PCM to control the position of the pintle with a high degree of precision. A pintle position sensor monitors the position of the pintle.
4. If there is too much EGR flow at idle, cruise or during cold running conditions, the engine will stop after a cold start, stop at idle after deceleration, surge during cruising speeds or idle roughly. If there is too little EGR flow, combustion chamber temperature can become too high during acceleration or under a heavy load, which can cause spark knock (in gasoline engines) and/or engine overheating.
Component replacement Gasoline engines
EGR valve
Note: The EGR valve is at the rear of the left cylinder head on 3.7L V6 and 4.7L V8 models. It is at the front of the right cylinder head on Hemi engines.
3.7L V6 engine
5. Disconnect the electrical connector from the EGR valve (see illustration).
16.5 Disconnect the EGR valve electrical connector (1), remove the EGR pipe flange (2), then remove the EGR valve bolts (3) (typical V6 or V8 engine)
6. Remove the EGR pipe mounting flange bolts.
7. Separate the pipe from the EGR valve, then pull it out of the intake manifold. Remove the gasket and discard it.
8. Remove the EGR valve mounting bolts and remove the EGR valve. Remove and discard the old gasket.
9. Clean the EGR valve mounting surfaces on the cylinder head and on the valve itself.
10. Installation is the reverse of removal. Use new gaskets between the EGR valve and the cylinder head and between the EGR pipe mounting flange and the EGR valve. Tighten the EGR valve and EGR pipe mounting bolts securely.
4.7L V8 engine
11. Remove the throttle body resonator.
12. Disconnect the EVAP system purge hose and the brake vacuum hose from the intake manifold.
13. Disconnect the wiring from the EGR valve (see illustration 16.5).
14. Remove the EGR valve mounting bolts and remove the valve along with the attached EGR tube from the cylinder head. Discard the gasket.
15. Remove the EGR tube from the EGR valve and discard the gasket.
16. Installation is the reverse of removal. Use new gaskets between the EGR valve and the cylinder head and between the EGR pipe mounting flange and the EGR valve. Tighten the EGR valve and EGR pipe mounting bolts securely.
Hemi engines
17. Disconnect the wiring from the EGR valve.
18. Unbolt the EGR tube from the EGR valve, separate them and discard the gasket.
19. Remove the EGR valve mounting bolts and remove the valve from the cylinder head. Discard the gasket.
20. Installation is the reverse of removal. Use new gaskets between the EGR valve and the cylinder head and between the EGR pipe mounting flange and the EGR valve. Tighten the EGR valve and EGR pipe mounting bolts securely.
EGR pipe
Note: The EGR pipe connects the EGR valve to the intake manifold.
21. Remove the engine cover.
22. Remove the EGR pipe mounting flange bolts. Remove and discard the old EGR pipe mounting flange gasket.
23. Disconnect the EGR pipe from the intake manifold.
24. Remove the old gasket from the EGR pipe flange and replace it with a new one. Remove the old seal (s) and gaskets from the EGR pipe. To ensure a positive seal, you should always replace them whenever you disconnect the EGR pipe.
25. Clean the EGR pipe mounting surfaces on the EGR valve and on the EGR pipe mounting flange.
26. Installation is the reverse of removal. Tighten the EGR pipe mounting flange bolts securely.
Diesel engines
EGR valve
Note: The EGR valve is at the front of the engine, on top of the intake manifold.
27. Remove the cover from the EGR crossover tube.
28. Loosen the left clamp and remove the right clamp from the EGR crossover tube.
29. Remove the bolt from the center bottom part of the crossover tube.
30. Disconnect the wiring from the EGR valve assembly.
31. Remove the four EGR valve mounting bolts.
32. Pry off the EGR valve assembly and remove it.
33. Clean all sealing surfaces of old gasket material and replace all gaskets.
34. Clean the EGR valve as well as the pipe and all other accessible parts (see Tune-up and routine maintenance).
35. Installation is the reverse of removal.
EGR cooler 6.4L Hemi and Diesel
36. Diesel models incorporate an EGR cooler that uses engine coolant to cool the hot exhaust gases to a temperature where they will better do their job of reducing combustion temperature when they are routed into the engine.
6.4L Hemi models
37. The EGR cooler is located under the intake manifold.
Diesel models
38. The EGR cooler/bypass valve assembly is mounted on the top of the exhaust manifold on the passenger’s side of the engine.
All models
39. Refer to Chapter Tune-up and routine maintenance for the removal and cleaning procedure.