what possible causes what technically would make a cel for o2 go off ONLY on long decleration in-gear?
keep getting one, and there's a noticable problem with the ignition tone, especially at higher rpm's(louder exhaust, therefor easier to hear), but it usually only happens when cruising. it appears as though cylinders 2&3 are leaning out also, based on what the spark plugs look like.
already replace both o2's.
already checked the wiring for the o2's.
obd0 pr3 b16a


Modified by freak86 at 3:40 PM 8/7/2007

 

You might have got a bad O2 sensor. Have you checked them out?

O2 cel's can be caused by a few things... Going too lean/rich is one of them. A O2 wire with a bad connection would.

Mine would only come on when at a heavy load for over a minute.
I have had them stick at a certain voltage too without a cel.

I would back probe the ECU connector for the O2 voltage and see if it is getting to the ECU.

 

the odds that i had the same problem with two different o2 sensors back-to-back is very slim, and not an option for serious consideration though i can't rule it out.
and like i said...i already checked the wiring.
voltage shows that the o2b sensor is leaning out(very low voltage).
so, if a/f ratios and bad wiring/sensors are the only thing that causes o2 cel's, then what can cause bad a/f ratios besides o2 sensors/wiring?

 

Long Decel in gear... Hmmm....you pull alot of vacuum when decelerating.

Map sensor might be your problem. Maybe.

It is a O2 code right?

Go thru the checks on the MAP with motor off. Atmospheric pressure. then with engine running would be estimated vacuum at 19in.hg. if using a vacuum pump.
Then to simulate decel check it at 30in.hg. with pump.

Now I am leaning towards MAP.

 

yes, it is a o2 code, but only for cylinders 2&3(i have to o2's. one's reading fine, and not causing 1&4 to lean).
how do i test the vacuum? is the pump what i need to buy? i'm a noob when it comes to vacuum

 

also, i do have one vacuum hose disconnected, as i cannot find anywhere to hook it up, and i have not found a correct diagram for the obd0 b16a vacuum yet. see my thread at:
https://honda-tech.com/zerothread/2065114

 

You do have the vacuum line plugged off. I know you have it plugged off.

What I think is happening is your 2&3 are lean and this is throwing the code
Too lean. So we can cross off the O2's they are correct.

Map... You can check the voltage with the key on engine off. Then start it and check your voltage. I don't have my book so I don't have the voltages that they are suppose to be. Strike that I found them in another book

Key on engine off the map voltage should be between 2.7v - 2.9v
Key on engine on the voltage should be between 0.9v - 1.1v maybe just a little over it is OK.

 

yeah. now would be the part where i say it was stupid of me to not plug off that hose, but i was under the intention of finding out where it goes, not plugging it off. it just hasn't happened yet, as i haven't found where to put it.
yes, 2&3 are leaning out. you are also correct that it's not the o2 sensors.
and guess what i found out today:
there is (what appears to be) coolant leaking out of, and around(in small amounts), the 2nd lower exhaust manifold nut/bolt that bolts to the head. how can i tell? i finally got the dang heat sheild off, and there's a stain from "some" fluid coming from that bolt area, and down the mani(ie: coolant leaking, and flowing down the mani). that would also explain the exhaust/steam that has been showing up in small emounts near the mani when the car starts to warm up. and when i turned on the car to see if more fluid was coming out, there was some little tiny bubbles coming from the little slits in the nuts on that bolt. i am going to assume that this is a HEAD GASKET LEAK! i also found that there was residual coolant/exhuast mix on the block below the mani(probably from the same source). however, i have not been dropping coolant from the car, so it's not alot, but it is bad enough to make me worry. i have not been losing alot of coolant, nor do i see any coolant in my oil, but that doesn't mean some isn't there in a small amount. i'm going to buy a new headgasket. man, i've only put on about 10,000 miles since the japan import. guess i'm just not lucky in this case. i'll keep ya posted on what happens.
thanks for your replies, and if you find a diagram for that vacuum, i'd be interested in seeing it.

 

It sounds like you could have misfiring injectors. Check for bad connections or clogged injectors. Also check the cap, rotor, and plug wires.

 

cap rotor and spark are all new earlier this year. spark plugs might need to be changed though after this problem, as i leaned out for a while on 2, and i've got some carbon buildup on the other two. this will come soon. got new ngk wires to go on it today.
already checked the injectors. that was right after the o2 checking. swapped the injectors, and the same problem existed. so, my money's still on the head gasket, as i just said before your reply. thanks for the suggestion though.

 

Try a compression and a leak down test for the head gasket diagnosis.