Initial Inspection and Diagnostic Overview

Visual Inspection Chart:

INSPECTION and VERIFICATION

NOTE: Exhaust system performance complaints such as excessive back pressure are usually noticeable by their effect on the performance of the engine. However, other malfunctioning components may have similar effects on the performance of the engine and be characterized by the same symptoms or complaints. It is, therefore, necessary to refer to Powertrain Management/Computer Controls/Testing and Inspection for diagnosis and testing of the engine. For general exhaust system complaints, refer to the Symptom Chart and Pinpoint Tests before removing and replacing any parts.

1. Visually inspect exhaust manifold, exhaust inlet pipe, Three Way Catalytic Converter (TWC), and muffler for cracks, leaks, punctures, improper welds or split seams. Replace components as necessary.

2. Visually inspect the components of the TWC and exhaust system and related controls that may affect exhaust gas quality or cause backfire or loss of power.

3. Check for broken or loose clamps, brackets or fasteners. Check all flanges between exhaust system components for loose fasteners and damaged gaskets. Tighten or replace as necessary.

4. Inspect wiring, connectors, and other components for obvious concerns due to looseness, corrosion, or other damage. This must be done when the engine is fully warmed so as to activate the system controls.

5. Check the vacuum lines and connections for looseness, pinching, leakage, splitting, blockage, or other damage that may cause malfunction.

6. If a vacuum line or orifice (restrictor) blockage is suspected as the obvious cause of a concern, correct the cause before proceeding to the next step.

7. Check engine oil for fuel dilution.

8. If all checks are OK, proceed to the Symptom Chart.


EXHAUST LEAKAGE or NOISE

NOTE: In the event of a three way catalytic converter failure, always check the muffler to be sure converter debris has not entered the muffler.

- External leaks in the exhaust system are often accompanied by noises and exhaust fumes. A visual inspection of the exhaust system will usually determine the location of a leak. When checking for exhaust leakage or noise, inspect the entire system for burnout holes and loose or corroded exhaust pipe flanges. Examine the underbody for greyish-white or black exhaust soot which indicates exhaust leakage at that point. For small leaks, have an assistant hold rags over the muffler outlet pipe while listening for the leak. This helps magnify the leak.

- When testing for a rattle or vibration condition, it is helpful to use a rubber mallet. Tap on the exhaust components to simulate the bouncing action of the exhaust, while watching for exhaust-to-body/chassis contact. Also look for loose or damaged heat shields or exhaust pipe flanges.

- Lightly tapping on the muffler and TWC can determine if there are loose or broken baffles in the muffler or a loose or broken element in the TWC.