Fuel/Air ratio problems...

[wht99civicex]

I have a 1999 Honda Civic EX D16Y8. Only mods include cai, header, catback. I am having a gas milage problem. My car is getting 20mpg or less depending on the week. The codes that come up are low voltage on O2 sensor 1 and fuel bar malfunction. Any input would be great, but I think the problem is directly related to the O2 sensor. Also my back bumper is littered with carbon, I thought it was oil... There are no signs of melting and its not just around the tip thats effected. The whole back of the car is black!

[Chiovnidca]

Can you post the actual trouble codes?

[wht99civicex]

Trouble Codes:

P0131
H-O2s low voltage (heated oxygen sensor bank 1 sensor 1)

P0170
Fuel Trim Bank One

P0171
Fuel Trim Bank One Condition

[Chiovnidca]

Originally Posted by wht99civicex

Trouble Codes:

P0131
H-O2s low voltage (heated oxygen sensor bank 1 sensor 1)

P0170
Fuel Trim Bank One

P0171
Fuel Trim Bank One Condition

It's most likely a bad o2 sensor, but, it may be a good idea to check the wiring for damage.

P0170 isn't listed for your car.

[kommon_sense]

Looks like you need to replace the o2. It would also explain the bad gas mileage. I have an oem primary o2 from my 98ex w/d16y8. PM me if you are interested.

[Raceready07]

smoke and or carbo could be a sign of bad valve guides. oil is getting on the back of the valve. I think that your 02 sensor problem is the engine is not burning all the fuel that it is spraying timeing could be to retar/adv. check it out let me kno



P.s Get a AEM adjustable fuel pressure regulator stop dumping gas

[wht99civicex]

The engine was recently rebuilt some im betting the guides are okay. I replaced the o2 sensor and the light went away for about a week. Before I replaced the o2 sensor I was getting a low voltage reading, and after I replaced the sensor it is reading high. I am a little confused because it was fine for a week. My gas milage seems to be back to normal, but the light is still on. Any suggestions?

[quicksweepEX]

it may have been rebuilt but was the head rebuilt, sounds like an 02 sensor,

[wht99civicex]

The head was not rebuilt... The o2 sensor has been replaced once, possibility that its bad again? I did end up getting one from www.oxygengeeks.com and it was really cheap. Is there a place I can take my car for a fast diagnostic run? The problem is I dont have a lot of time, it would need to be done on my lunch period. I'm pretty good when it comes to replacing parts, but figuring out whats wrong with it is not in my cards. Autozone will run my obdII codes, but that doesnt seem to be helping I keep getting a high voltage reading on my primary o2 sensor.