I have a 98 EX Coupe, and my fuel economy's gone down the drain. I've noticed though, it's been running a little rich because I can totally smell gas coming out of the exhaust.

I was wondering if I have a bad O2 sensor or maybe because I have an ebay Hi-Flow Cat with the o2 sensor ports on the opposite end, so I only have the 1 O2 sensor at the headers and the other one isn't connected at all.

Strangely, my check engine light never went on after I installed the cat. Can anyone help me with this?

 

i have the hi flow cat too and it made my engine come on. b/c mine was doin the same thing runnin rich. does the engine light comeone when you turn your key on? b/c your light would be on not havein a cat

 

well, you have an OBD2 setup then... if your 2nd o2 sensor isnt "plugged in" then your ECU isnt getting the proper reading to create the proper air to fuel ratio. That is the reason you have bad MPG now. Take it to an exhaust shop and have them install the 2nd sensor into your exhaust... shouldnt cost more than 10-15 dollars. or you could just buy the bung($5-7) and have a muffler shop install it for like $5, they usually do it on the side if you tip the welder.

 

ok, thanks for the advice, I'll try that. No, my engine light doesn't turn on at all. I think (but I'm not sure) there might be a leak in the cat at the O2 sensor port (because the o2 sensor port is on the wrong side of the cat, the wire's not long enough on my 2nd o2 sensor to reach it). I'll check back here when if I still have a problem.