I was checking my oil a few days ago and noticed about a 2 inch crack in my DC Sport 4-1 header on my 2005 Civic with the D17A2 engine. They will not honor their warranty on their 4 month old expensive POS, but anyway, I have a 2.25 inch Ebay exhaust system and test pipe, if that matters. The car seems to run fine, but when I rev it, I can hear the exhaust coming out of the crack. Will this affect performance, fuel econony or cause valve damage, or just be louder? Do I need to do something about this, or can I just drive it? Thank you, and have a great holliday.

 

It's up to you whether or not you want to continue to drive like that.

The answer to your question is Yes to all except for the will not be any "valve damage". The crack will be negative in all aspects.

Be smart to replace it, (Warranties are for workmanship. Cracks mean it was more likely not installed with flex springs in the catalytic converter area, which is considered user-error. )
Replace it with your stock one for now, and move on.

 

your o2 sensor is now sensing fresh air and telling the ecu to dump more fuel than necessary into the engine the longer you leave it the worse it will get dude just replace it

 

I do not have a stock one, a friend bought it, and I can not afford to replace it right now. Should I unplug the upstream oxygen sensor so it does not run it rich?

 

Unplugging that sensor will throw an O2 sensor error code via the ECU, and the car will simply run worse.
Time to either remove it to have it welded by a professional, or find another used OEM for now.


Next time you get an aftermarket piece, wait a year before selling the older OEM part you're replacing it with. That's Rookie Season modification rule 102.

 

It is hard to turn down $100 for a stock exhaust manifold. He is still learning...

 

Where is the crack in the header?

 

It is mostly in the cylinder 2 tube, but a little at the collector also.

 

Easy fix, pull it out and take it to a sheet metal shop that does tig welding. They can have it fixed in a day or so and it shouldn't be that much money out of pocket.

 

I'd betcha he'd trade that $100 back right now to keep driving while he finds a solution at his choosing.

 

Yet another story of a DC Sports header being junk and cracking. I can't believe they are still in business.

https://www.google.com/search?q=dc+s...honda-tech.com

 

Because they have deals that Honda guys just can't refuse!!.

They've been around over 20 years just for Hondas alone.. They'll be around longer other than some cracked header.....

 

Had a crack in my OE header. The O2 sensor was pissed about it and made the ECU dump fuel to account for the additional surprise air. So this lead to CAT failure since it is not designed to burn up raw fuel.

In the meantime, it was idling like crap and the MPG went in the toilet.

Replace the header.