Restricted Exhaust

Diagnostic Aids

Warning: In order to avoid being burned, do not service the exhaust system while it is still hot. Service the system when it is cool.

For dual exhaust systems a quick check of exhaust flow will help determine which side of the exhaust system is restricted. The side that has less exhaust flow is the side that will be suspect, and diagnosis should begin there.

Note: This will not apply if the dual exhaust is equipped with an “H” pipe or similar configuration in which the exhaust flow would be equalized.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. The exhaust system has very low back pressure under normal conditions. If the exhaust system is restricted, a significant increase in the exhaust pressure is noticed on the J-35314-A Exhaust Back Pressure Gauge.
  2. This step will isolate the catalytic converter from the remainder of the exhaust system.
  3. Confirming that the condition has been fixed is essential. If the symptom still exists and the vehicle has a dual exhaust system, proceed to Step 2 and repeat diagnostic procedure on the opposite exhaust pipe.
Restricted Exhaust

Step

Action

Value(s)

Yes

No

1

Did you verify the customers complaint?

—

Go to Step 2

—

2

Did you review the exhaust symptoms diagnostic information and perform the necessary inspections?

—

Go to Step 3

Go to Symptoms - Engine Exhaust

3

Is the system equipped with dual exhaust?

—

Go to Diagnostic Aids

Go to Step 4

4

  1. Remove the secondary air injection (AIR) check valve or the heated oxygen sensor (HO2S) that is in front of and closest to the catalytic converter. Refer to the affected component’s service procedure.
  2. Install the J-35314-A Exhaust Back Pressure Gauge in place of the AIR check valve or HO2S sensor.
  3. Start the engine.
  4. Increase and monitor the engine speed at 2,000 RPM.
  5. Observe the exhaust system back pressure reading on the gauge.

Does the reading exceed the specified value?

14 kPa (2 psi)

Go to Step 5

Go to Step 8

5

  1. Turn the engine off and place the ignition in the lock position.
  2. Remove the J-35314-A Exhaust Back Pressure Gauge.
  3. Re-install the AIR check valve/HO2S sensor. Refer to the affected component’s service procedure.
  4. Remove the post-catalyst HO2S sensor. Refer to the affected component’s service procedure.
  5. Install the J-35314-A Exhaust Back Pressure Gauge in place of the post HO2S sensor.
  6. Start the engine.
  7. Increase and monitor the engine speed at 2,000 RPM.
  8. Observe the exhaust system back pressure reading on the gauge.

Does the reading exceed the specified value?

14 kPa (2 psi)

Go to Step 6

Go to Step 7

6

Inspect the exhaust system for the following conditions:

  • Damage in the exhaust pipe
  • Debris in the exhaust pipe
  • Muffler or resonator internal failure
  • Two-layer exhaust pipe separation

Did you find and correct the condition?

—

Go to Step 8

—

7

Replace the catalytic converter. Refer to the affected component’s service procedure.

Did you find and correct the condition?

—

Go to Step 8

—

8

  1. Remove the J-35314-A Exhaust Back Pressure Gauge.
  2. Reinstall the AIR check valve or the post-catalyst HO2S sensor. Refer to the affected component’s service procedure
  3. Clear any codes.
  4. Road test the vehicle in order to verify the repair.

Did you correct the condition?

—

System OK

Go to Step 2