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exhause smells bad, bad gas mileage too

2580 Views 19 Replies 13 Participants Last post by  Chris Fiorelli
Sup pplz.

i have a 94 civic dx with a super bad smell coming out the exhaust. a friend of mine told me the smell is like unburned fuel which i believe would explain my bad gas milage too.

i hooked up an air/fuel ration to it (at the o2 sensor) and the guage stays stuck on rich.

they car only recently started doing this.. i have also noticed that sometimes the check engine light goes on.. but when i turn off the car and turn it back off its gone, so i cant get an ecu reading.

what would cause this.. and what can i do to fix it.
is it the o2 sensor?

its a 94 civic dx, sohc non-vtec
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bad rings maybe? i have no clue go get a compression check?
does it smell like rotten eggs or something?
yup.. now that i think about it. it does smell a little like rotten eggs
Probably the O2 sensor, and if it's been happening for a while, that smell might be a dirty converter from the rich mixture. They have been known to put off that eggy aroma.
klungemonger said:
Probably the O2 sensor, and if it's been happening for a while, that smell might be a dirty converter from the rich mixture. They have been known to put off that eggy aroma.
Agreed. Bad cat's small like rotton eggies. Might be time for a new cat...among others things to fix your rich mixture.
my car ('94 dx sedan) also smells like eggs, but only when I push it hard, i figure the smell is the cat, but cat problem could be caused by o2 sensor. MSN carpoint states that the o2 sensor is a problem area for civics of that year.
Update on this

well.. took my car out of storage yesterday and started fixing the egg smell problem.

i changed out the Cat, distributor cap and rotor, o2 sensor. and today im swapping out the cables, plugs and fuel filter.

i dont know what else it can be?.. i know its running too rich, its just how to tone it down is the hard part

any ideas?
Have you driven it yet since you did all that work? Perhaps you need to remove battery cables for like 10 minutes or so. I think that resets the ECU so it will start operating properly from the inputs from the new sensor and stuff, sort of "reconfigure" itself.

On another note, are you sure your afr meter is alright? I would drive around starting with a full tank and when it's empty figure out what yoru mileage is. You should be able to tell by that if your really too rich also...
KoolAsian said:
New Cat my man! :D
He did that, I just want to know if he's driven or tested it since he installed it.
well.. i changed cables, plugs, fuel filter and i drove it around. problem seems to have fixed itself but now the a/f guage is steady on lean even if i bail on it.. it will light up about 4 notches or so and thats it. i removed the guage and tryed it in a different car and it worked fine there so i know its not the guage.

well.. im taking it to inspection tomorrow so ill know for sure if it passes or not. other than that im going to buy a fuel pressure regulator so i can adjust it.

im going to also try filling up the tank and running it till its on fumes.
Hondas are set to run lean from the factory, that's partly how they get those great emissions ratings! Best mixture for performance is like 12:1 or so, honda runs I think at over 14:1 afr. Just ballpark figures, nobody flame if I'm a bit off... The old VX could operate at up to 24:1 ratio!!! 56 mpg on the freeway, but not much for accelerating.
definitely runnin rich.. check the plugs and ignition stuff (distribitor, wires, and so on)
oh yeah.. timing might be off too
h82lose said:
Sup pplz.

i have a 94 civic dx with a super bad smell coming out the exhaust. a friend of mine told me the smell is like unburned fuel which i believe would explain my bad gas milage too.

i hooked up an air/fuel ration to it (at the o2 sensor) and the guage stays stuck on rich.

they car only recently started doing this.. i have also noticed that sometimes the check engine light goes on.. but when i turn off the car and turn it back off its gone, so i cant get an ecu reading.

what would cause this.. and what can i do to fix it.
is it the o2 sensor?

its a 94 civic dx, sohc non-vtec
This post is OLD SCHOOL.
help?

My gas mileage got really bad too, I have a 95 civ sedan DX. It's been this way for about a month and I can't figure it out. A full tank last about 3 days (usually less) and I know it should last way longer. I changed the wires, rotor, and cap, and my platinum plugs are fairly new (aug./sept.). I have an exhaust resonator on it and I even reset my ecu. After reading your posts I'm wondering if it could be the o2 sensor and/or the fuel filter.

Is there any way to know if these are my problems without changing them?

Can anybody help me out about changing the filter? Are there any sites that go it detail about changing a fuel filter?
its pretty easy to change a filter... located on the firewall to the left of the intake mani... just remove the bracket and remove the bolt on top and on bottom...be care though. some fuel will spew out of the lines

then do reverse procedure for the new one

hope this helps
My Si started the same thing last night, but my CEL popped up too :eek:
well to reset the ecu at the battery unhook the ground (black) for 30 seconds.. dont get a fuel pressure regulator.. as far as i know the lowest pressure on those is still higher than stock

props to the 88 91 recaro hatch
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