DanVB1
New member
- 15
- 6
- 3
- Buick Ownership
- Encore
Had the dreaded P0420 code (catalyst efficiency).
Crawled underneath the car to check for any visual signs and voila! The flex joint on the exhaust pipe from the upstream converter was loose!
Bought a new pipe for about $150, changed the old one and it worked, no more code.
A few notes:
The old pipe is a bear to get off, make sure to support the car properly with a jack stand at the right location (not the floor pan).
Spray the rusted nuts with penetrating oil, let soak a bit. It takes a lot of muscle to loosen them (I strained a rib muscle while pulling the breaker bar).
I luckily found both new gaskets at the O'Reillys, they were cheap. The old gaskets are thin plates, they looked good but probably wouldn't seal well. The new were thicker, sandwich style with a good amount of crush to seal.
The front uses the studs attached to the cat, the rear I used (2) new SS bolts/nuts/washer/lock washer.
I also replaced the downstream oxygen sensor that is screwed into the new pipe. I figured I've gone this far, what's another $70?
So far, so good.
Crawled underneath the car to check for any visual signs and voila! The flex joint on the exhaust pipe from the upstream converter was loose!
Bought a new pipe for about $150, changed the old one and it worked, no more code.
A few notes:
The old pipe is a bear to get off, make sure to support the car properly with a jack stand at the right location (not the floor pan).
Spray the rusted nuts with penetrating oil, let soak a bit. It takes a lot of muscle to loosen them (I strained a rib muscle while pulling the breaker bar).
I luckily found both new gaskets at the O'Reillys, they were cheap. The old gaskets are thin plates, they looked good but probably wouldn't seal well. The new were thicker, sandwich style with a good amount of crush to seal.
The front uses the studs attached to the cat, the rear I used (2) new SS bolts/nuts/washer/lock washer.
I also replaced the downstream oxygen sensor that is screwed into the new pipe. I figured I've gone this far, what's another $70?
So far, so good.