Hey Guys,

i've never had a problem with this, but i'm stumped, my hydrocarbon reading at idle is off the charts.

Cruise limit: HC: 400 ppm CO: 3%
Cruise measured: HC: 185 CO: 0.99
Idle limit: HC: 400 ppm CO: 3%
Idle measured: 2462 ppm CO: 3.32%

i changed out my wideband o2 sensor because it had stopped feeding info after the first fail, i changed out my spark plugs and oil and added a can of guaranteed to pass to the gas after the second fail.

now i am wondering if my wideband o2 sensor is feeding crap information to the ecu, even though it is reporting a nice stoich 14.7 at idle and cruise (2500 rpm).

too many hydrocarbons means too much fuel right? I have a high flow cat on my car, it should be ok..

thanks for any ideas, i'm getting frustrated here.. my next step is putting stock o2 sensor back in and feeding it to the ecu instead of the wideband's narrowband output that currently feeds it. all three tests have given me the same results so far so i've not hit anything right yet.

Marko

 

Dude,


You could have a leaky/sticking injector, bad plug wire, weak spark, bad ECU, etc. Have you check for error codes? Make sure the individual injectors are firing. A bad coolant temperature sensor that the ECU uses could cause it to think the coolant is colder than it is and the engine never goes into a closed loop (reading O2 sensor data), thus is runs rich all the time. It could be a combination of factors; it's too early to rule out anything at this stage.



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i have live feedback from the wideband o2 and it says my air fuel ratios are fine (14.7), but i wonder now if it is bs-ing me. and i suppose it could be a single injector or plug wire causing it in one cylinder and that might make it miss the o2 sensor reading too.. time to dig into those details.

 

Dude,

It could be 14.7 overall, but remember that you're seeing an average of multiple cylinders; if one is leaking/not burning fuel properly, you could easily miss that as the ECU leans out the other cylinders to compensate. All of this happens in milliseconds, too fast for your O2 sensor gauge to adjust. Make sure the injector plugs actually click into place. A lot of them become brittle with age and will no longer click and lock as they're supposed to.



Good luck

 

I have never had any luck using the widebands narrow band signal to the ecu, it never works right, even if it kinda works it does not do a good job. I wouldn't even bother doing more troubleshooting till I changed that. I would strongly recommend you connect a stock o2 sensor for the ecu, and do not split the signal from one o2 to 2 pins on the ecu, you need one o2 for each like stock (unless you run a JDM GTE ECU then there is only one o2 total), and just use the wideband as a monitor, that is what I do on my car. make sure your tps is in the correct position and the idl pin is activated, check by seeing if you a check the timing, engine should change sound when you put the jumper in the diagnostic port or else the tps is off or bad. this does not allow the car to truely "idle" and fueling can become erratic.

thats quite high on the HC, that usually comes from unburnt fuel. you could have a slight misfire issue due to whatever reason and the wideband wont always pick it up, but the fuel will show up on the sniffer. you can even be running a little rich and pass as long as there isn't a misfire which makes HC shoot up.

you ever hear any popping at idle?

 

i have a stock exhaust so i'll have to listen extra hard, the 350z trans rattle covers the exhaust noise lol.

i had a coworker tell me the same thing about widebands, i will give it a shot. the JZX100 motor only has one o2 sensor and i didn't have any problem feeding the narrowband signal from wideband on my 240sx with a ka24de so i'm just surprised that it doesnt work well with this.

i put the stock o2 sensor back in yesterday to feed the ECU, will verifiy with the obd1 logger that it is activating correctly and then off to try again i go. i'll listen for misfires first too, was hoping new plugs would cure that if it was happening.

time to weld a second bung on the downpipe for the wideband then.. never ending list with this car!

thanks!
Marko

 

well that was it, i passed emissions with stock o2 sensor. chalk one up for the records for anyone else having trouble with a wideband simulating the narrowband and idle emissions

 

Dude,


What brand of wide-band O2 sensor, with narrow-band output, are you having trouble with? Some of them require a recalibration after a certain number of miles.


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i have an innovate LC-2 wideband that i am feeding the narrowband to the ECU and wideband to an arduino+display to show digits. Neat solution with the arduino and display, about 20$ and you have an AFR readout

i used a PLX M300 in my 240sx (discontinued at this point) and never had this issue. must be a toyota/nissan ecu thing or just a difference in how the widebands work. Both widebands i had hooked up on the downpipe right behind the turbo and with the innovate that is another thing that it doesnt like, the manual says to put it as far downstream as possible so it doesnt overheat, i already lost one sensor with it, so in a way it is good that i have to put the stock o2 back on and relocate this guy.

but yes, the innovate does require calibration, and i've done that, even put a fresh innovate sensor on it because i thought i had cooked the old one and it made no difference (that was my second test failure).

Marko

 

glad you passed, I knew it right away when you said that, never tried it on a nissan but on my stock sc300 ecu it did not work at all whatsoever, that was on an aem wideband using the blue narrowband wire. always keep the stock o2 sensors for the toyota ecu's and then add other stuff as extra.

I'll give my personal theory on the subject, I think it has to do with the rate of switching, even though the wideband says narrowband output that only means 0-1v, there are a bunch of other things that need to be correct also for the ecu to accept it, and often the ecu doesn't like it.
the reason it was fine emissions wise at a load is cause the "burn" is more forgiving off idle to extra fuel, so that extra fuel was being burnt up.