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Pinpoint Test 1: Restricted Exhaust System Test

PINPOINT TEST 1 - RESTRICTED EXHAUST SYSTEM TEST

PINPOINT TEST 1 RESTRICTED EXHAUST SYSTEM TEST
STEP INSPECTION ACTION
1 EXHAUST SYSTEM INSPECTION
  • Inspect the exhaust system for damage or deterioration. Look for cracks, punctures, leaks, loose connections, dents or unusual bending.
  • Is the exhaust system OK? 
 Yes Go to next step.
No REPAIR or INSTALL any damaged or deteriorated exhaust components. TEST the system for normal operation.
2 VACUUM TEST - MUFFLER DISCONNECTED
  • Connect a vacuum gauge to the intake manifold vacuum source.
  • Connect a tachometer.
  • Disconnect the muffler. Support the exhaust system.
    NOTE: Monitor the speed the vacuum gauge needle rises, while increasing the engine RPM.
  • On a non-restricted exhaust system, the vacuum gauge needle rises quickly to the normal range as the increased RPM is maintained.
  • On a restricted exhaust system, the vacuum gauge needle rises slowly to the normal range as the increased RPM is maintained.
  • Start the engine and gradually increase the engine speed to 2,000 RPM with the transmission in NEUTRAL.
  • Is neutral vacuum greater than 53.8 kPa (16 in-Hg.)? 
 Yes The restriction is in the muffler assembly.
INSTALL a new muffler.
See MUFFLER AND TAILPIPE REMOVAL/INSTALLATION - 2.3L for 2.3L engine.
See MUFFLER AND TAILPIPE REMOVAL/INSTALLATION - 3.0L for 3.0L engine.
See MUFFLER AND TAILPIPE REMOVAL/INSTALLATION - 4.0L for 4.0L engine.
Test the system for normal operation.
No Go to next step.
3 VACUUM TEST - CATALYTIC CONVERTER(S) DISCONNECTED
  • Turn the engine OFF.
  • Disconnect the catalytic converter(s) from the exhaust manifold. Support the exhaust system.
  • Repeat the vacuum test.
  • Is the manifold vacuum greater than 53.8 kPa (16 in-Hg.)? 
 Yes Replace the three-way catalytic converter.
See THREE-WAY CATALYTIC CONVERTER REMOVAL/INSTALLATION - 2.3L for 2.3L engine.
See THREE-WAY CATALYTIC CONVERTER REMOVAL/INSTALLATION - 3.0L for 3.0L engine.
See THREE-WAY CATALYTIC CONVERTER REMOVAL/INSTALLATION - 4.0L for 4.0L engine.
Test the system for normal operation.
No Go to next step.
4 VACUUM TEST - EXHAUST MANIFOLD(S) DISCONNECTED
  • Turn the engine OFF.
  • Disconnect the exhaust manifold(s).

See EXHAUST MANIFOLD REMOVAL/INSTALLATION - 2.3L for 2.3L engine.
See EXHAUST MANIFOLD RIGHT HAND REMOVAL/INSTALLATION - 3.0L for 3.0L engine.
See EXHAUST MANIFOLD LEFT HAND REMOVAL/INSTALLATION - 3.0L for 3.0L engine.
See EXHAUST MANIFOLD RIGHT HAND REMOVAL/INSTALLATION - 4.0L for 4.0L engine.
See EXHAUST MANIFOLD LEFT HAND REMOVAL/INSTALLATION - 4.0L for 4.0L engine.
  • Repeat the vacuum test.
  • Is the manifold vacuum greater than 53.8 kPa (16 in-Hg.)? 
 Yes REMOVE the exhaust manifolds. INSPECT the ports for casting flash by dropping a length of chain into each port. Do not use a wire or light to check ports. The restriction may be large enough for them to pass through but small enough to cause excessive back pressure at high engine RPM. REMOVE casting flash. If flash cannot be removed, INSTALL new exhaust manifolds. TEST the system for normal operation.
No Go to next step.
5 CHECK FOR ADDITIONAL SYMPTOMS
  • Connect all disconnected components.
  • Perform PCM Quick Test.
  • Are any DTCs present? 
 Yes See DTC INDEX - POWERTRAIN CONTROL MODULE (PCM)  .
No See SYMPTOM TROUBLESHOOTING CHART - ENGINE MECHANICAL  for diagnosis and testing of the engine.
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