How to Install a Primary Catalytic Converter on Acura TL: Step-by-Step

Quick answer

Replace the primary catalytic converter on an Acura TL by disconnecting the battery, soaking the O2 sensors and flange bolts with penetrating oil, removing the old cat, and installing the new one with fresh gaskets. Use a 7-layer turbo-to-downpipe gasket if your setup uses a factory-style flange, and torque all fasteners to factory specs to prevent exhaust leaks and check-engine lights.

Replacing the primary catalytic converter on an Acura TL is a straightforward job if you plan for rusted fasteners and gasket sealing. The primary cat sits close to the engine, so it sees extreme heat cycles that can make bolts brittle and gaskets hard. Working on a cool engine and using the right gaskets and torque values will save you from chasing leaks later.

This guide walks through the process from preparation to first start, with checkpoints for common mistakes. It applies to typical Acura TL models where the primary cat is integrated with the exhaust manifold or downpipe, and it covers O2 sensor handling, gasket selection, and final torque.

Preparation and safety

Park the car on level ground and let the engine cool completely before touching exhaust components. Disconnect the negative battery terminal to protect the ECU and avoid accidental short circuits when you unplug O2 sensors. Raise the front of the car and support it with jack stands. Spray penetrating oil on the O2 sensor threads, flange bolts, and any heat shield fasteners, then let it soak while you gather tools.

You will need a basic metric socket set, extensions, a breaker bar, an O2 sensor socket or crowfoot wrench, and a torque wrench. Have new gaskets ready. If your TL uses a turbo-to-downpipe style flange, a multi-layer stainless gasket such as the PLM Subaru Turbo to Downpipe Gasket - 7 Layers can work well because its 7-layer 304 stainless steel fire-ring design resists blowout, though verify the port shape matches your flange.

• Never work on a hot exhaust; burns and warped flanges are common.
• Label O2 sensor connectors if you unplug more than one.

Access and removal

Remove any plastic undertrays or heat shields that block access to the primary cat. Unplug the upstream and downstream O2 sensors from their harness connectors, then thread the sensors out of the pipe. If a sensor is seized, use a proper O2 sensor socket and apply steady force rather than impact tools, which can crack the ceramic. Next, remove the bolts connecting the cat to the manifold or turbo outlet and the bolts at the rear flange.

Support the exhaust with a jack or stand before removing the last fastener so the pipe does not drop. Once free, pull the cat out carefully. Inspect the old gaskets and flanges for warping or cracks. If the flange surface is pitted, a thicker multi-layer gasket can help fill minor imperfections, but severe warping requires resurfacing or replacement of the mating part.

• A breaker bar with a six-point socket reduces the chance of rounding rusted nuts.
• Keep the old gaskets for comparison; note the port shape and bolt pattern.

Installing the new primary cat

Clean the flange surfaces with a wire brush or scraper to remove carbon and old gasket material. Install new gaskets dry unless the manufacturer specifies a sealant. If you are using a 7-layer gasket like the PLM Subaru Turbo to Downpipe Gasket - 7 Layers, its 304 stainless steel fire-ring and 7-layer construction are designed to handle high heat and pressure, but it must match the flange geometry. Hand-thread all bolts first to avoid cross-threading, then snug them in a star pattern.

Reinstall the O2 sensors with a small amount of high-temperature anti-seize on the threads, being careful not to contaminate the sensor tip. Route the sensor wires away from hot exhaust surfaces and secure them with the factory clips. Reconnect the battery negative terminal after all electrical connections are made.

• Do not reuse old gaskets; they harden and will not seal twice.
• Anti-seize on O2 sensor threads makes future removal easier.

Torque and first start

Torque the flange bolts to the factory specification for your Acura TL. If you do not have the exact spec, a common range for exhaust flange bolts is 25–35 lb-ft, but always prioritize the manufacturer's value. Torque in stages and in a crisscross pattern to compress the gasket evenly. For O2 sensors, tighten to the spec, typically around 22–33 lb-ft, or snug plus a quarter turn if no spec is available.

Start the engine and let it idle. Listen for exhaust leaks at the flanges and check for a check-engine light. A leak will sound like a rhythmic puffing or hiss. After the engine cools, re-check the torque on the flange bolts, as heat cycles can loosen them. If a leak persists, inspect the flange for warping and consider a thicker gasket or resurfacing.

• A second torque check after one heat cycle prevents most leaks.
• If a CEL appears, scan for O2 sensor codes before replacing parts.

Installation steps at a glance

1. Cool and disconnect: Let the engine cool fully, disconnect the negative battery terminal, and raise the car on jack stands. Working on a hot exhaust risks burns and warped flanges.
2. Soak fasteners: Apply penetrating oil to O2 sensors, flange bolts, and heat shield bolts; let soak for 15–30 minutes. Rushing this step often leads to broken bolts.
3. Remove O2 sensors: Unplug connectors and thread sensors out with an O2 sensor socket. Never pull on the sensor wires; they break easily.
4. Remove old cat: Support the exhaust, remove flange bolts, and pull the cat out. Inspect flanges for warping. A dropped exhaust can damage the flex pipe or oil pan.
5. Clean and install new gaskets: Clean flange surfaces and install new gaskets dry. Hand-thread bolts before tightening. Reusing old gaskets is the top cause of leaks.
6. Reinstall O2 sensors: Apply high-temp anti-seize to threads and route wires away from hot surfaces. Contaminated sensor tips cause poor fuel trims.
7. Torque in stages: Torque flange bolts to factory spec in a crisscross pattern; torque O2 sensors to spec. Uneven torque warps flanges and causes leaks.

Products that fit this job

• PLM Subaru Turbo to Downpipe Gasket - 7 Layers: 7 layers of stainless steel with a 304 stainless steel fire-ring; 200% thicker than other aftermarket gaskets and 22% thicker than OEM Subaru gaskets; references Subaru part number 144022AA180. If your Acura TL exhaust flange matches this gasket's port shape, the multi-layer stainless construction resists blowout better than a thin single-layer gasket, especially on high-heat turbo or manifold connections.
• PLM Power Driven Honda Civic Turbo 1.5T Front Pipe 2022+: Crafted from 3-inch stainless steel with TIG-welded construction; bolts onto PLM downpipe or factory downpipe and exhaust system. This is an example of a direct-fit stainless front pipe, but it is specific to 2022+ Honda Civic 1.5T, not Acura TL. Use it as a reference for material quality and fitment style when shopping for TL-compatible parts.

Installing a primary catalytic converter on an Acura TL is manageable with the right gaskets, patience with rusted fasteners, and a torque wrench. Always verify fitment for your specific model year and engine, and use new multi-layer gaskets to avoid comebacks. If you are unsure about O2 sensor placement or torque specs, consult a service manual for your TL.