How to bypass a catalytic converter

Written by thomas west
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A catalytic converter is essential to your vehicle's emission system; it functions by transforming "raw" exhaust into less environmentally damaging gases. There are few instances in which it is allowable to remove the catalytic converter and install a bypass pipe. If a vehicle has high mileage, the converter can become clogged, causing the vehicle's performance to suffer; a bypass pipe then is installed in place of the converter as a troubleshooting tool to see if the vehicle's performance returns to normal with the converter removed.

Skill level:
Moderate

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Things you need

  • 2 auto ramps
  • 2 wheel chocks
  • Penetrating fluid
  • Adjustable wrench
  • Bypass pipe

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Instructions

  1. 1

    Pull the vehicle onto a pair of auto ramps and set the parking brake. Place wheel chocks under the rear wheels. Allow the car to cool if it has been run recently.

  2. 2

    Crawl under the vehicle and spray penetrating fluid onto the holding bolts on each end of the catalytic converter (the converter is located on the exhaust system near the front of the vehicle) and allow it to work in for a few minutes.

  3. 3

    Unplug the oxygen sensor wiring harness from the converter (if equipped). Loosen and remove the converter holding bolts with an adjustable wrench, in a counterclockwise direction, and set them aside.

  4. 4

    Lower the converter to the ground and set it aside. Place the bypass pipe into the exhaust system where the converter was removed. Use the original converter bolts to attach the bypass pipe, and tighten them with an adjustable wrench in a clockwise direction.

  5. 5

    Remove the wheel chocks and back the vehicle off of the ramps. Road test the vehicle. Re-install the original converter or install a new one in place of the test pipe in the reverse order.

Tips and warnings

  • If you have installed a bypass pipe on your vehicle, remember to replace the catalytic converter as soon as possible. Your vehicle will not pass an emissions test without the catalytic converter.
  • Small gains in engine power may be achieved by bypassing the converter, but check your local laws before bypassing your catalytic converter. Some states may allow the use of a test pipe in off-road situations, such as racing.
  • Be aware that the vehicle's exhaust note may be louder with the converter bypassed.

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