What's up HT,

Got my car about 3 weeks back. 00 Civic Si. Car has 67k miles. Car was surging/misfiring. Had the CEL for it so i decided to do a full tune-up. Wires, spark plugs, etc.

After the tune-up, CEL light came off and car wasn't misfiring/surging anymore. All was good. Drove the car for about 100 miles to a friend's house and my CEL goes on again. Check the code and it's a P0420 "Catalyst System Efficiency Below Threshold (Bank 1)."

Decided to start from the top and checked out my exhaust manifold. I found a crack inbetween cylinder #2 and #3.

Do you guys think this crack can be allowing air to throw my sensor off which is giving me this P0420 code? I'm really hoping it's not my catalytic converter. We all know how expensive that is..

 

That will definitely cause the p0420 code. If you want to be cheap just go get some muffler cement from the auto parts store. You'll have a heat shield over it so who cares.

How do I know that'll cause it? My wifes 00 civic had a cracked manifold by the o2 sensor and it threw the code...good thing I b swapped n turbo'd the civic. I had another manifold in the garage and I just swapped it in.

Oh make sure there are no other leaks furthur down the exhaust system.

 

That will cause the P0420. You can try some band aid fixes (reseal crack, O2 simulator, spark plug defouler) but start looking around for a replacement.

 

"Got my car about 3 weeks back. 00 Civic Si. Car has 67k miles". Hope you know the guy you bought it from as the speedometer and odometer could have been disconnected a long time ago to hide true mileage.

Anyway, don't waste money on welding it as it won't last long. Replace with after-market and hope that existing front o2 sensor is removable without stripping it's threads.

 

Thanks y'all. Ima have my cat and pipes checked for extra measures if the problem extends.

Do you guys recommend that I just upgrade to let's say DC Headers? Rather then going to OEM. Just an idea since I'm already deciding to change it.

 

There's no real reason to, other than cosmetics. It's all personal preference.

 

There's much better headers out there for the money of a DC. The OEM route is going to be pricey unless you go used.

 

Dc sucks, but get whatever your budget can afford. Its just a d series. No real power will come out of it if you're going N/A

 

Yeah the OEM one would cost me about $200. Was thinking of just upgrading them but i don't have much knowledge on headers. Just heard DC was pretty common.

Sounds good brah. It's actually a B-Series.