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CHAPTER 50

CHAPTER 50. Induction and Exhaust. Inspecting the Throttle Body, Air Induction System, and Intake Manifold. 50-1. Start the engine and let the idle stabilize. Using an acetylene or propane testing tool, place the hose near the suspected leak area.

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CHAPTER 50

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  1. CHAPTER 50 Induction and Exhaust

  2. Inspecting the Throttle Body, Air Induction System, and Intake Manifold 50-1 • Start the engine and let the idle stabilize. Using an acetylene or propane testing tool, place the hose near the suspected leak area.

  3. Inspecting the Throttle Body, Air Induction System, and Intake Manifold 50-1 • Open the fuel valve to slowly release the acetylene or propane.

  4. Inspecting the Throttle Body, Air Induction System, and Intake Manifold 50-1 • On vehicles without an idle control system, observe the rpm and smoothness of the engine. If the engine speed increases or smoothes out, then a vacuum leak is present. Determine any necessary repairs. On vehicles with an idle control system, connect a scan tool and select data stream. (continues)

  5. Inspecting the Throttle Body, Air Induction System, and Intake Manifold 50-1 • Observe the oxygen, short-term fuel trims, and injector pulse width as you are moving the acetylene or propane around.

  6. Inspecting the Throttle Body, Air Induction System, and Intake Manifold 50-1 • Shut off the engine and connect a smoke machine to the intake manifold. Start the smoke machine and inject smoke into the intake manifold.

  7. Inspecting the Throttle Body, Air Induction System, and Intake Manifold 50-1 • Using a bright light, look around the engine compartment for traces of smoke. Any smoke coming from the air cleaner inlet is normal. Determine any necessary action(s).

  8. Testing the Idle Air Control Operation 50-2 • Connect a scan tool that is compatible with the vehicle you are working on, and start the engine. • Compare the desired idle speed to the actual idle speed. The speeds should be very close to each other. • Locate the output commands function in the scan tool. • Command a step-up of the idle speed and verify that it does so smoothly. Complete the same process for stepping down the idle speed. If the system is not operating correctly, follow the steps in the service information to diagnose the fault. Determine necessary actions.

  9. Inspecting the Exhaust System for Leaks 50-3 • Raise the vehicle on a lift and secure it in place. Use a drop light to inspect for leaks or rust holes in the exhaust system. Check the exhaust manifolds for evidence of exhaust leaks.

  10. Inspecting the Exhaust System for Leaks 50-3 • Have a helper hold a rag against the exhaust pipe(s) while the engine is idling to increase the pressure in the system. Listen and feel for any leaks.

  11. Inspecting the Exhaust System for Leaks 50-3 • Use large adjustable pliers to test the integrity of the pipes by moderately squeezing the pipes. Determine necessary repairs.

  12. Testing the Exhaust System for Back- Pressure 50-4 • Remove the oxygen sensor. Install an adapter to the oxygen sensor hole and connect a low-pressure gauge.

  13. Inspecting the Exhaust System for Leaks 50-4 • Start the engine and observe any exhaust back-pressure, which should be no more than 1.5 psi (10.3 kPa) at idle and no more than 3 psi (20.7 kPa) at 2000 rpm. Increase the engine rpm to 2000 rpm and observe the pressure. Determine any necessary actions.

  14. Inspecting the Exhaust System for Leaks 50-4 • Inspect the oxygen sensor gasket, put anti-seize on the sensor threads, and torque to the proper specifications.

  15. Performing an Operation Test of a Turbocharger/Supercharger System 50-5 • Connect a vacuum/pressure gauge to the engine intake manifold and route it under the hood and through the passenger window, or tape it securely to the windshield. • Drive the vehicle in a safe place and in a safe manner. • Observe the pressure rise and compare it to the manufacturer's specifications. Determine any necessary actions.

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