My car has been running rich since i installed a mini me, and im still on the bunny trail trying to locate the part that is causing this. I have been throwing code 43 every once in awhile as it is only on 10% of the time i am driving, meaning that sometimes it comes on and sometimes it doesnt. I bought a new bosch o2 sensor from the auto part store. It was plug and play for the obd1 civic dx. I am still throwing the code once in awhile and gas milage hasn't improved. So i am not sure what i need to do at this point, here are the parts i have replaced so far.

Distributor, Plugs, Plug wires, o2 sensor (still have code), ecu.

As far as performance it runs perfect but its getting 24 mpg.
I don't know what else could be causing this bad gas milage, please help honda-tech

 

Are there any odd symptoms? A high idle? Soot on the bumper? Are you missing any vacuum lines or could one have a hole in it? It sounds like a situation I had when my MAP sensor was not hooked up. It ran fine but a high idle and soot on the bumper and 27 or so MPG's.

 

43 isnt necessarilly an o2 code.
there are no mods to the car?

 

Funny thing is, my car's exactly like that. Stock 98 sedan, o2 sensor went out so I replaced with brand new one, been running perfect but gets 24 mpg all the time. In for an answer

 

Fuel filter?

 

Wouldn't a bad fuel filter stop fuel from getting to the motor? Not give extre fuel. I have no codes right now. Mods are intake and header. I have no black soot on the bumper. Cmon guys I know there are
some awesome mechanics on here that could diagnose this

 

check fuel pressure, check for exhaust leaks before o2, what you need is a scan tool to see what the o2 is doing.

 

Code 43 is pretty tricky, I'd start by testing the tps and map sensor.

 

A plugged fuel filter will decrease gas mileage. Most people would think that because it's restricting flow that the car will not get as much fuel and get better fuel economy. This is wrong. Basically the restriction in the system is making the fuel pump work harder, and when it's able to get the fuel passed the restriction it's generally pushing too much fuel. Basically it's not allowing the system to function at the pressure it should be. Also, plugged fuel filters are very very hard on fuel pumps.

I myself would never buy the cheapy oxygen sensors, let alone a Bosch one. What you need to do is see if the oxygen sensor wiring and connector are functioning correctly. The oxygen sensor can't do it's job properly when it's getting the wrong signals.

 

http://downloads.hondatech.info/Auto...e%20Manual.zip
right click & save as target
thats the helms manual. go to fuel & emissions and go through the diagnostic chart. should be able to help you pinpoint your problem.

 

hit up sparkplugs dot com get yourself a NGK or Denso O2 sensor and probably cheaper than the bosch.

 

Im no longer throwing the code, i installed an oem used sensor. So i know the fuel filter has been replaced but im not sure how long ago mayybe i will try that next.

 

Great stuff... Thanks alot i will see that i can find.