4.8t

i have a 97 civic with a b16a. i'm getting like 20mpg and burning rich as crap. its all stock beside cai. and a walbro high flow fuel pump. its runing a jdm computer. can a bad o2 sensor cause this bad of mileage? how far can the honda fuel trims swing? and how can you reset fuel trims on these? my car for what ever reason will not comunicate with a obd2 reader. for a cel i have to use a jumper and count the blinks. yes its odb2 i never swapped over.

rick_rabies

yeah if the o2 sensor is out or broken the ecu makes changes i think stock o2 narrow band goes to 12sih to 14ish thats it.
your plugs can be the problem too
use some fuel cleaner
and get a usdm ecu
and replace your cat. (gut it or put a resonator in it)
tire pressure

4.8t

well the plugs go bad cause it so rich. new plugs will be black in a matter of minutes. cat is gone already. tire pressures are good. by d16y8 got 40mpg on highway. this one is no where near that. and i am pretty sure its the o2 sensor. if it was a modded ecu i would go there but its stock. oh did i mention the back of my car turns black with in a couple days of driving. and oil smells of fuel by drain time.

rick_rabies

check oil consumption and compression test.
try putting in a new o2 sensor. bad o2 sensor/or none shouldnt cause it to be that bad

zedron

iTrader: (1)

Sounds like an one of the O2 sensors to me. Did it always drive liek this or just one day it started? When my O2 went on my Integra, it dropped my mileage from 29/30 to 16/17. I was like wtf is going on, because it didnt even throw a code.

4.8t

its started when i did the motor swap. there are no codes and the wireing is correct. the y7 motor got 36ish on high way then i went to a y8 and it got 40+ and now the b16 and it sucks. i used the o2 sensor that came with the motor. i sold my y8 so i couldn't put that o2 sensor in.

rick_rabies

get a new o2 sensor and try that.

4.8t

i think i will. how can i reset fuel trims so it doesn't foul the sensor on first start up?

slow.ek.hb

o2 sensor

rick_rabies

new plugs and reset the ecu. unplugn the batery and waitn like 30 seconds

91rangerturbo

check your fuel pressure also. I know sometimes dropping in a walbro you can get higher pressures and it will change your base pressure. Go ahead and verify that isn't a issue also.

4.8t

i thought about the fuel pressure thing also. but its not as easy as say my tahoe, where it has a Schrader valve to hook up to.

man i cannot stand not having tuning/dataloging ability. on my tahoe i can alsways find out whats going on. i have a computer i'm about to mod so i can tune it. then wire the thing up and be on my way.

yessewey

iTrader: (2)

im pretty sure i read a thread not too far back about a guy who was getting horrible gas mileage too (it was a long thread) and it turned out to be his fuel pump because he had a walboro 255 also, replaced it and problem solved.

zedron

iTrader: (1)

If you are using stock injectors having a high flow pump can be a problem because it can over power your FPR and force more fuel to the injectors causing them to over fuel the sytem. This happens on cars where the factory FPR is startign to get a little old and wears out.

yessewey

iTrader: (2)

well i found the thread and well, enjoy reading lol.

https://honda-tech.com/forums/showth...16+gas+mileage

4.8t

so the return line on these are big enough to flow the amount to be return? as in its usually a regulator issue not the fact that the return line is small. i was told there is a fitting to buy to help check fuel pressure. are they on ebay or what?

96honda_EK

Check the tp sensor. Its right on top of your intake manifold. I had this problem with my eg once. The problem was that i was missing a little gasket under the tp sensor. It was running hella rich. Like gas was spitting out of the exhaust. So check that out

ek4_b16a

and your scanner tool can't read the computer because you are running an obd1 ecu i'm guessing?! it's an obd2 scanner so it won't be able to read your ecu. you can jump the lil clip on the same side as the ecu to read your codes that way.

4.8t

that should be the map sensor on top. i've swapped it out already. no gasket ("O" ring) would make it think there was no vacuum and yes that would cause it to run rich. i've adjusted the tp sensor which is on the side of the tb. its on the side because its driven by the tb shaft thats driven by the throttle cable.

in the first post i said its obd2. its not obd1, i know its not obd1 because i did the wiring myself. the harness is my stock obd2 harness modded to run v-tec. when i get time i'm going to swap the o2 sensor out and check fuel pressure. i may swap the stock fuel pump back in just to see what it does.