Oxygen Sensor On 87 Accord Carbureted

[Hondaisok]

What purpose does the oxygen sensor serve on an older Accord? There doesn't seem to be an ECU as such as on an EFI model, or on the 1990 and later models. Other cars I have owned, it can cause idle problems, and I understand it is the #1 cause of failure of the smog test. However, I have read most of the posts on this site, and rarely see it mentioned.

[russiankid]

it is used for emissions, but if it isnt working, it wont harm anything, you wont even know about it till emissions

[Hondaisok]

Thanks for the info. I am still trying to figure out this site.

[VTEC_Inside]

it is used for emissions, but if it isnt working, it wont harm anything, you wont even know about it till emissions

Thats the first time I've heard that. Most seem to think that it doesn't affect very much at all.

I should probably change mine if you are correct, I'm going to be e-testing mine again within the next week or so.

[TheWatcher]

IIRC, the carb ECU controls the fuel maps, if your o2 sensors are not working right, your fuel economy will suffer (ECU uses 411 from o2 sensors).

Gas is expensive, so if you KNOW the o2 sensors are bad, replace them.

AFAIK, the oem o2 sensors are the best, aftermarket are cheaper, but not supposed to be quite as good (based on post(s) that I have read).

BTW, if you are concerned about replacing something, I would definitely replace the fuel filters before the o2 sensors (cheaper, probably in more need of replacement). Carbs have 2 fuel filters, I have replaced both of mine (normal maintenance).

Peace.

[SiR]

I have the original o2 sensor and have 322k miles. Its pretty useless, still runs good with respectable mileage.( bet it hasent worked in 15 years) HAHAHA, Florida kicks ass!

[russiankid]

haha i live in new orleans, and all your car ahs to do to pass inspection is it cant ahve a cracked windsheild, all lights work, ur windsheild wipers have to work and your horn, thats it

[SiR]

haha i live in new orleans, and all your car ahs to do to pass inspection is it cant ahve a cracked windsheild, all lights work, ur windsheild wipers have to work and your horn, thats it

Sweet, gotta love it.

[lostforawhile]

ok i've mentioned this a hundred times,but it does affect the way your car runs,the carb car does have an ecu,it's under the drivers seat,and yes it does control the carb, the carb computer allows precisly controlled amounts of air to enter the intake manifold controling the mixture, thats what those big white valves are that attach to the intake. this is the simplified version of how it works, it uses that oxygen sensor as the main judge of what the air fuel mixture is, the carb is set rich from the factory,the air entering the intake sets it very lean. this is controlled from that 02 sensor,a barometric pressure control valve under the fender,an electronic temp sensor in the air cleaner air snorkel,a switch in the speedometer head that tells it when you ae going over 15 miles an hour,and a bunch of other parameters, it is a combination electronic and mechanical vaccume system that all works together. or is supposed to. the carb computer can also raise the idle through an idle control acuator on the side of the carb, and a solonoid valve, it senses rpm through the same circuit that the tach uses. the main problem with the carb computer is that is has no diagnostics, so your best bet is to replace that sensor at specified intervals. oh i almost forgot it controls the system that allows extra oxygen into the exaust manifold through the air injejection system, if this doesn't work properly it can ruin your converter. it also causes you to fail emissions. I've been working on these systems for years and it still does stuff that baffles me sometimes, the local dealer won't touch them with a ten foot pole, and whoever designed it was smoking something really strong.

[VTEC_Inside]

I guess getting a new O2 sensor would be a good idea for me then since I just put on a new cat.

My mileage has remained fairly consistent over the 5-6yrs I've owned the car though. If it was running rich I would have expected a decrease.

[lostforawhile]

it's possible your sensor might have been installed before you got the car,if the system is running right it is probably fine, the mixture is not normally rich,the air pulses the computer allows into the manifold set it lean, the other reson for that system is to allow the use of a three way converter on the car, the only way to use one on a carbed car is to control the mixture very closely. that valve with the metal tube on it that goes to the exaust manifold, the one right behind the valve cover,that allows clean filtered air from the air cleaner to be pulled into the exaust manifold in precisly controlled amounts. this helps the converter work better. everything is set from the mixture read off of that o2 sensor. plus the other parameters of course,but mostly from that sensor. it's a crazy system from a time in the eighties that used to be called emissions control hell.

[VTEC_Inside]

I always wondered what that metal tube was for.

The O2 sensor still concerns me a bit on my car. I failed the etest in '04 because of high CO which would seem to indicate rich mixture. I have a feeling that it had much more to do with the car not comming up to full running temp at the time. I think I may crack out my multimeter and see what the sensor is feeding.

[lostforawhile]

ok here are a couple of pics,this is the carb computer that noone seems to know about,it's under a plastic cover under the drivers seat. it will say solonoid valve control unit, it's still a basic computer because it uses inputs from different parameters to adjust outputs. years ago in tech school they were called logic controlers.

this is the part that confuses everyone, it attaches to the air cleaner on one end,and on the other end attaches to the valve that allows air to enter the exaust manifold. all it is is an air distribution point,it's empty there is nothing inside of it. the wierld little plastic piece between it and the air cleaner is just a tube with a silencer on one side of it. this allows clean air into the plastic box, then it distributes that air to the solonoid air control valves and to the reed valve for the exaust. the metal tube coming off the exaust is nothing more then an old fashiond tube for a reed valve. just like the reed valves that have been on cars since the seventies. the only difference is that the computer turns this one on and off at high speed to allow pulses into the exaust.

[Hondaisok]

Darn, I should have remained ignorant. Sounds like too much going on for me to check. As long as it passes smog check, as we call it, I think I will go on pretending it doesn't exist.

[lostforawhile]

the main thing to check is the 02 sensor,it's a simple one wire one, thats he source of most of the problems with the control system,the other one is misrouted or cracked or disconnected vaccume lines. if the lines look brittle,replace them with new vaccume hose one piece at a time,to avoid confusion, usually the lines near the control box are fine it's the ones near the engine that get bad. especially check the litle short hoses at the base of the carb in the back. they crack easy from the heat and can cause all kinds of problems. they are about an inch long and there are three of them.

[VTEC_Inside]

How does one go about checking the sensor. The service manual doesn't appear to give any instructions on doing so, and I can't find anything regarding what the output of it should be.

[2drSE-i]

its pretty difficult. you need a specific socket, and it may take some time to break loose. from what you said about a carb o2 sensor, i gather this from my EFI ones

My o2 sensors being bad is causing my efi car to run ridiculously rich, because my efi computer is not reading how much oxygen is actually running to the combustion chamber, so it feeds more and more fuel. correct?


edit:
i strongly belive (and hope) this is the only thing wrong with my car, but i filled up today and found that i only got 20.5 mpg, which is pathetic with our cars, even carbed ones. i wouldnt think that my distributor could be bad, the car only has 117k miles on it. dude i vote sticky on this thread, and post any info on efi cars u can. Tim is the coolest

[VTEC_Inside]

I'm inclined to think that my O2 sensor is still working somewhat properly. My mileage has not really changed over the entire time I've owned the car.

If I knew what the sensor should be outputing I could check it with my multimeter.

[VTEC_Inside]

Ok, I believe I've finally found the answer I was looking for.

The O2 sensor will actually generate voltage between 0-1v based on mixture. Approximates are rich if over .5v lean if under .5v.

Will have to check the thing tommorow.

[VTEC_Inside]

Ok, I just checked mine. Once warmed up its hovering around .10-.13 or lean.

I'm inclined to think that is pretty normal because I've never had any emissions trouble at idle.

Once I rev it up though it seems to sit steady at .89 which is probably as rich as it can read.

The sensor reacts very quickly from idle to rev and vice versa.

I'm probably etesting mine again this week, but if its still showing high CO this time, I'm pretty much out of ideas as to how to correct it.

[lostforawhile]

its pretty difficult. you need a specific socket, and it may take some time to break loose. from what you said about a carb o2 sensor, i gather this from my EFI ones
My o2 sensors being bad is causing my efi car to run ridiculously rich, because my efi computer is not reading how much oxygen is actually running to the combustion chamber, so it feeds more and more fuel. correct?
edit:
i strongly belive (and hope) this is the only thing wrong with my car, but i filled up today and found that i only got 20.5 mpg, which is pathetic with our cars, even carbed ones. i wouldnt think that my distributor could be bad, the car only has 117k miles on it. dude i vote sticky on this thread, and post any info on efi cars u can. Tim is the coolest

yea this could be causing that these are very early electronic fuel injection systems, i'm not sure if they have a default map or not, it may not show a code if it's within range and it's stuck at a particular reading. when they get old they sometimes stick at a rich or poor reading,in other words the computer thinks it's withinnormal parameters and it's blindly trying to adjust for it. it's pretty common for a car with an early fuel injection system to become a gas hog with a bad sensor. a modern honda computer would have detected that the fuel map wasn't changing with different load and rpm but these early ones are almost blind. remember they are not that far advanced from pac man and atari 64 game systems.

[2drSE-i]

hehehe thanks man



STICKY THIS THREAD

[lostforawhile]

bleep!bleep!blep!bleep!beep!blop!buzz!dam accord ate a ghost again

[VTEC_Inside]

ghost?

[lostforawhile]

well i figured out these used all the unsold pac man games for the computers in our cars at least on the carb cars