Removing Cat Converter

Welcome to TW! Why do you want to remove the cat?

 

The OEM cats on the Tacomas are a "High Flow" honeycomb type of cat. Many tests have been done to see the difference between them being on vs. off, and no gains have been found one way or the other.

 

"back pressure" and Scavenging are 2 different things. The OEM exhaust system has hardly any "back pressure" stock.

 

Cats dont rob hp. The older ones did, but newer ones dont.

 

• Idle smoothness. Check for any signs of surging or roughness, indicating misfire or improper fuel delivery.

• Check the tailpipe, particularly immediately following start-up, for any smoke indicating too rich AFR (black smoke), water/antifreeze (white Smoke), or oil (blue smoke).

• Listen to engine carefully for any signs of vacuum or exhaust manifold leaks.

• Inspect intake system for signs of oil indicating excessive blow-by or cracks that may cause leaks.

• Inspect spark plugs/wires and air filter.

• Scan tool test.

• Do not reset MIL light!!

• Read the OBD-II readiness tests to ensure all tests have been completed. If the tests have not been completed, chances are the MIL was recently reset, possibly hiding intermittent problems.

• Read trouble codes (if any) and inspect as necessary.

• Read pending trouble codes (if any) and inspect as necessary.

• With engine running and at operating temperature, read scan data list. This is typically a table listing all available sensors and outputs.

• Look at Long Term Fuel Trims (LTFT). These show the amount (in %) the computer is modifying fuel delivery, based on the 02 sensor feedback. Positive numbers indicate the computer is adding fuel, negative numbers indicate the com­puter is removing fuel. Large positive numbers (>10%) should be investigated further as they indicate the computer is adding more fuel than originally designed.

• Look at the O2 sensor output signals. Sensor 1 is before the converter, Sensor 2 is behind the converter, Bank 1 and 2 are typically used in V-configuration where Bank 1 is on the side Cylinder 1 is located. Some inline 6 cylinder engines have Bank 1 as Cylinders 1-3 and Bank 2 as Cylinders 4-6. The sensors are usually abbreviated as O2S1B1 (O2 Sensor, Bank 1)

• Sensor 1 output should be very active and oscillate rapidly from approximately 0 to less than 1 volt. If the signal tends to show high voltage with little fluctuation, excessive unburnt fuel is reaching the sensor. If Sensor 1 shows low or no voltage, the sensor could be defective, or there might be an exhaust leak in front of or immediately behind the sensor, or there could be a lack of fuel delivered to the combustion chamber. If the sensor does not respond to a rapid accelerator kickdown, chances are the sensor is defective. If it does respond, an exhaust leak or lack of fuel is indicated. (The preceding test must be done after the engine and exhaust system have been allowed to fully heat up.)

• Sensor 2 should show a fairly steady signal. It is not critical what the signal is, only that it does not oscillate as frequently as the front. If the signal is above 250mV, the sensor is fine. If it is below, check for activity by rapid accelerator kick-down or by raising the engine speed to approximately 2000 rpm. Any movement indicates the sensor is fine.

• The most important thing to remember about Oxygen Sensors is that they were never meant to last the life of the car! They are wear items and need to be replaced as you would brakes, tires or spark plugs. When Oxygen Sensors reach 80,000 miles plus...change them. Catalytic Converters do not go bad by themselves, 95% of the time some other issue with the vehicle will destroy the cat and most of the time it is the Oxygen Sensors. Even when you have them checked and the tech says they are operating okay...if the mileage is over 80,000 change them. When sensors reach that age they may still be functioning but the signal they send becomes lazy and since they operate in millivolts the slightest signal fluctuation can cause an air/fuel mixture problem and that in turn will take out the cat. If you are in the market for a converter and the vehicle still has the original Oxygen Sensors you should strongly consider their replacement...if not you could be buying another converter 90 days down the road.

 

ITS NOT BACK PRESSURE!!!!!


ITS SCAVENGING!!!!!


*looking thru fridge for beer*