Hey i just bolted a 4-2-1 header onto my 96 civic dx d16y7 but i just ordered my highflow cat so it just goes to a test pipe right now and no cat also my second o2 sensor isnt attached because i need to buy a new one and extend the wires to the bung on the high flow cat. Could this be why im getting no power? Because the 02 sensor isnt attached or because i have a test pipe instead of a high flow cat? All i know is it is installed correctly and the its really loud i also get backfire with it and im not sure why. I need to know if hooking up the 02 sensor will get my power back or if i need to do the cat as well. I torqued them all down to 25 and im almost positive the 02 sensor has something to do with it because it talks to ur ecu also it smells bad it supposed to for the first little while like u can really smell the fumes when i rev it and sit in the same place its also putting out white smoke. Please let me know thanks

 

Are you getting a code? Sounds like it's running very rich, which could be caused by an O2 problem.

 

yea im getting an oxygen content code cuz one o2 sensor isnt even plugged in. Could that be the reason for it running rich? please let me know thanks

 

That would be the reason. Those oxygen sensors are essential.

 

i had a testpipe mated up to a large diameter exhaust on my crx. it was mad loud and it also smelled a little bit. since my o2 sensor comes before my cat (b16), i dont have the ecu problem and im also running stock ex. manifold. ive heard hondas need some back pressure or else power can actually decrease. i switched to a gutted cat from a testpipe. belive it or not, the sound was cut down a lot, no more backfiring, and no more smell (almost).

 

No no no no no no no...

Back pressure is a side effect from reaching a reasonable compromise between maximizing exhaust velocity and CFM of exhaust. Engines do not "need" back pressure, it just happens that no exhaust possible will flow 100% of the exhaust an engine produces while simultaneously keeping exhaust velocity high for best scavenging effect, without generating some back pressure.

Back pressure impedes the flow of exhaust, and on a little four cylinder, you want to move the exhuast as efficiently as possible so that the maximum amount of fresh air/fuel mix possible is brought into the cylinder for combustion.

 

i [might] stand corrected

 

not having the second )2 is making you run in limp mode. Get that thing hooked up and you'll get your power back.

 

your computer has no clue on how rich or lean the engine is running without the O2 sensor. so it uses a preset fuel map that is set quit rich on hondas.

 

I think you've all missed something here... Regardless of the electronics side of the equation, there is the smoke. If you are running rich, the smoke will be BLACK. If burning oil, BLUE. And if you are burning coolant, the engine will produce WHITE smoke. Do a leakdown test to find out if you have a blown head gasket...