# Exhaust Back Pressure and Emissions **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [December 17, 2025, 5:36pm UTC](https://community.cartalk.com/t/exhaust-back-pressure-and-emissions/204639 "2025-12-17T17:36:24Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![jmcarc](https://avatars.discourse-cdn.com/v4/letter/j/278dde/32.png) [@jmcarc](https://community.cartalk.com/u/jmcarc)\ **Post date:** [December 17, 2025, 5:36pm UTC](https://community.cartalk.com/t/exhaust-back-pressure-and-emissions/204639/1 "2025-12-17T17:36:24Z")
My 2005 Buick Century with 353k miles gets a recurring P0420 code, catalytic converter operating below efficiency level. Twice this year, I tried using Cataclean, but with no success. I noticed a small hole in my muffler at the seam. Could a lack of exhaust back pressure cause the CC to operate inefficiently or improperly? Can anyone recommend a catalytic converter cleaner? Or, is it all snake oil? ---
**Author:** ![Mustangman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/mustangman/32/44130_2.png) [@Mustangman](https://community.cartalk.com/u/Mustangman)\ **Post date:** [December 17, 2025, 5:47pm UTC](https://community.cartalk.com/t/exhaust-back-pressure-and-emissions/204639/2 "2025-12-17T17:47:31Z")
No, lack of backpressure has nothing to do with your issue. You need a new catalytic convertor most likely ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [December 17, 2025, 5:54pm UTC](https://community.cartalk.com/t/exhaust-back-pressure-and-emissions/204639/3 "2025-12-17T17:54:04Z")
the muffler is after the catalytic converter. So a hole in the muffler isn’t going to effect catalytic performance. I know people go into denial, (and I ain’t talking the river), when this code appears, but in all the years being a mechanic this code always meant the converter needed to be replaced. Especially if the vehicle has over 300,000 miles. You just need to hook a scanner up and watch what the #2 O2 sensor is showing to confirm if the cat is bad. [![](https://global.discourse-cdn.com/cartalk/original/3X/9/2/920c82aae79279b7169d496b337e65aa8eb81476.jpeg "Using upstream and downstream oxygen sensors to test the catalytic converter") ](https://www.youtube.com/watch?v=KGpMzdEO5KY) Tester ---
**Author:** ![texases](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/texases/32/862_2.png) [@texases](https://community.cartalk.com/u/texases)\ **Post date:** [December 17, 2025, 6:32pm UTC](https://community.cartalk.com/t/exhaust-back-pressure-and-emissions/204639/4 "2025-12-17T18:32:33Z")
Yeah, likely the cat. How many miles do you go between adding a quart of oil? ---
**Author:** ![bcohen2010](https://avatars.discourse-cdn.com/v4/letter/b/779978/32.png) [@bcohen2010](https://community.cartalk.com/u/bcohen2010)\ **Post date:** [December 18, 2025, 7:20pm UTC](https://community.cartalk.com/t/exhaust-back-pressure-and-emissions/204639/5 "2025-12-18T19:20:57Z")
Well first of all, Cataclean is a product which you add to the fuel, so it gets burned in the engine. There is no chance in heck that this product could actually work to clean a catalytic converter. Assuming that the reason why the cat has lost effectiveness is a buildup of soot, etc. on the catalyst mesh, the only way to clean it is to unbolt and remove it, and clean with carburetor cleaner or a similar solvent. I have done this successfully to get a vehicle through emissions testing, but I suspect that even cleaning will only work for so long. At over 300,000 miles, I doubt cleaning would work, and assume the cat is worn out. As long as you don’t live in California, you can replace it for a few hundred bucks if you DIY. It should be noted that some states follow California emissions standards, and won’t allow a federal cat to be sent there, however I believe California is the only state where they physically verify that your cat has a C.A.R.B. number etched on it. ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [December 18, 2025, 7:39pm UTC](https://community.cartalk.com/t/exhaust-back-pressure-and-emissions/204639/6 "2025-12-18T19:39:15Z")
> [@bcohen2010](#): > > There is no chance in heck that this product could actually work to clean a catalytic converter. [![](https://global.discourse-cdn.com/cartalk/original/3X/5/d/5d9298a5468c8121cdb59ffe153b27e64bcc23ce.jpeg "CATACLEAN Catalytic Converter Cleaner | Does It work?! (Real Data) Before And After") ](https://www.youtube.com/watch?v=VcgaTlH2Z60) Tester