2005 Acura RSX - What did I do wrong?


I put new headers, Hugh flow cat and magna flow exhaust on my RSX, 05, automatic. Now my check engine light is on, and exhaust tip has black carbon. Code says bad O2 sensor bank1. I replaced both. What’s my next option?


Put it back to stock configuration.



What is this car talk for after market parts haters? Stock header had a hole in it and removing it ruined the cat down pipe. You must not be much of a mechanic if the only comment you have is a one liner saying some thing as simple as “put it back to stock” which is something my dad would say to me around thirty years ago. Anything original to say?


Never try to out-engineer the engineers that designed the engine.



Most of the Car Talk members are senior citizens. What is the fault code in Pxxx format?


Aftermarket parts aren’t hated. The problems they may cause are what gets the hate. There may be a technician who has the time and the experience to help you but you won’t find one everywhere you look. In the end you may find out that the only solution is to restore the car to manufacturers specifications. I would like to believe that other options will work but I don’t know where to start. I would like to know if the new exhaust came with any disclaimers which hint that “this changes everything.” You’re the professor now and if you solve the problem, this senior citizen would like to know how you did it. Proctology fixed my exhaust last week and I get a B12 shot this week. TMI we got.

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The code did NOT say bad 02 sensor, there is no code that says “BAD O2 SENSOR”

The code Pxxxx said that the O2 sensor detected a problem.

What is the code you are getting.


There are numerous O2 sensor codes. You are most likely seeing something like P0130 which means there is a problem with the circuit to the sensor. We need to know what code, or codes you are seeing in order to help you further with this.


Which would lead me to think the high flow catalytic converter might be the culprit. The cat-back aftermarket exhaust should not cause any problems.


He’s a good enough mechanic to recognize a jacked-up mod when he sees one.

I have nothing against mods, but when you screw with the parts of the exhaust where oxygen is measured, and then you get an oxygen-related code… I mean… It’s fairly obvious, to us anyway, what went wrong.

Why is this hard?


Most people who come here are either looking for advice offered for free or are willing to offer advice for free. You may or may not hear from a real mechanic here. That doesn’t mean the non-mechanics here are hacks.

The problem you have after the modifications may require a real mechanic. It’s up to you to search for and evaluate them. Good luck. Nobody here wishes you any harm or even inconvenience.


Purebred made a valid observation . He said he thinks the High flow catalytic convertor might be the problem and that is an entirely logical assumption. Maybe you should have listened to your father more often.


Cat back exhaust systems do not affect any of the engine systems. I have a custom fabricated cat back exhaust with FM 40s, no problems.
So simple, leave everything else as is but try it with a stock cat-may solve your problem. But, have it your way.


I’m not a real mechanic and don’t pretend to be but I have nursed cars for over a million and a half miles and have run into a lot of issues. I never do modifications though so have no comment. There are sites that cater to folks that do modifications. So all in all, I think we should just cheerfully refund the OP’s money.


But he DID get what he paid for… :sweat_smile:



An engine with Variable Valve Timing?

I wonder if there’s now a problem with over-scavenging of the cylinders?



Don’t let the door hit you in the backside on the way out.


One idea, the high flow exhaust is now blowing so much volume flow past the o2 sensors it isn’t allowing the o2 sensors to heat up to their designed operating temperature, making them inaccurate, and causing a problem with the engine’s air/fuel ratio. Overly lean or rich operation could easily result. There may be known solutions available to this sort of problem in the racing community. Surf over to Summit Racing, maybe they have posted some ideas there in their o2 sensor section.

You didn’t mess w/the fuel system components right? Just the exhaust? I think there may be a solution but we-folks here, most of us aren’t in the racing community. Some folks here are though.


You need to ignore the forum members that are here just to razz people and engage in discussion with the few that asked what is the specific fault code that you have.

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George, by trying to help this guy, you’re in effect excusing his behaviour . . .