So my check engine light came on. I checked it out and it pointed me towards the o2 sensor. So tonight, when I got home, I took the heat shield off and found this:



So, here are my questions. First, I'm assuming I need to replace the exhaust manifold because I can't drive around like this forever. How hard is that to do? I've done brakes, alternators, etc. but I've never done something like this. I couldn't find a diy about this so if you know of one I'd appreciate it. Second, is there a chance the sensor is fine? It's just getting this error because of the crack? I appreciate the help. Let me know if there is any info I forgot to include. Thanks.

 

Well if the manifold is cracked then one can only assume your o2 sensor took a dump with it. Exhaust manifolds are not hard to do at all. Just a matter of unbolting your manifold from your head, and your exhaust, and putting the new one in. If you ever wanted an excuse to put exhaust on your car now would be the perfect time since your manifold is shot anyway you could just slap a dc sports 4-1 header or what ever you fancy on it. I recommend replacing the o2 sensor, and gaskets when you replace your manifold.

 

Just unbolt from the head, Do it slowly so you wont strip the bolts (spray with WD-40 or something first).

There might be a bracket holding it in place as well, unscrew that.

Then unscrew the downpipe from the cat and pull it out as one piece from under your car.

I suggest changing the gaskets, and as for the O2 sensor check if you still get the CEL with the new exhaust manifold, if you do then change it if not then you're good

 

How much price difference is there between a stock manifold and an aftermarket? Also, how do the aftermarkets effect mileage? How do I tell what engine I have so I know what headers fit? Finally, I'm in WI so I have to pass emissions testing. How much does that limit my choices? Sorry for all of the noob questions.

 

If you're on a budget i'd suggest ebay, but people are gonna go against it because its not a name brand. It's $50 with gaskets, and downpipe.
A name brand header such as DC sports can range anywhere from a cheap $150 find on craigslist to $250-$300 new.
As for emissions, you should be fine, if your stock header has a O2 sensor then make sure the new one has an O2 sensor hole as well, and it should just screw right in.
And as for mileage, i'd think better air flow = better mileage.. but idk thats just my opinion.
You have a D16Y7(non vtec) since its a 99 civic lx.

 

Thank you so much for the info. So if I replace the header with a cheap ebay header and don't relocate the converter I should still be able to pass emissions as long as the o2 sensors are working? I was under the impression I would need the converter to pass. FYI WI uses the plug into the OBDII method of emissions testing.

 

You just replace the header and down pipe, that's just right before the catalytic converter. So the exhaust manifold just goes from the head, then it connects to the downpipe, (unless it's a one piece header), then drops down right before the catalytic converter and thats where you bolt it. You'll figure it out once you take the old one off.

 

Y7s have the catalytic converter integrated into the exhaust manifold. If you want to get rid of the Y7 manifold (understandable because they don't flow particularly well and they have tendency to crack where the O2 sensor screws in) you will need to run a cat and intermediate pipe for a '99 - '00 EX Coupe or Sedan. You will also need to extend the wires for the secondary O2 sensor.

 

So I might be confused. Is this the catalytic converter circled in the picture?

 

Thats it alright.

 

oh i forgot the Y7 has it in the exhaust manifold itself. Yeah you're going to have to get a cat from a 96-00 civic ex if you want to bypass that. Or just purchase a generic high flow cat on ebay..

 

Thanks for the help guys. I think I'm going to check the local salvage yard for a stock header/converter just to get by for the time being.

 

Sigh, the joys of the Y7...

 

But on the bright side, Pick-n-Pull is having their semi-annual 1/2 price sale this weekend. They've got 7 civics on the lot too. If one has my header it will only cost me $23 and some elbow grease. Good times!