FUBAR front 02 sensor?
 

I had a buddy of mine hook my 8 up to his expensive computer since mine is basic and we discovered that my front 02 reading stays below .05. The reason I checked this was because my car is running really rich (also worse gas mileage & misfires/power loss that isn't ignition related). Is my front 02 FUBAR?

If the sensor is sensing lean it would be making the car run rich...

Edited from the future, holy crap! Link to replacement AFR/02 is on Page 5.

Stays below .05 what?

Volts
Lambda
AFR

Yes the Front 02 sensors wear out

Ask your friend with the fancy computer to read the LTFT at idle (for curiosity and to see if you can do it)

edit
Are sure you're reading the O2 sensor?
Maybe .05 is a typo?
.6 lambda is like 8.8 afr (neighbourhood) soooo .05 is straight gasoline lol or a broke O2 sensor if it is the O2 you're reading

Volts, sorry about that! Forgot to put that lol. He said anything under .05 amps indicates a lean condition, and the car would be mistaken causing it to run rich. I'll go back over and get the LTFT and get back with you. Thanks!

Volts or Amps?

They are different, pretty sure you mean amps

He told me volts...I'll check with him again. Just finished cooling flush and I'm heading over there for the LTFT now

Ok so he said it's definitely volts. He also said it was inded the front 02. He also said it reads from .01 to 1.0 volts but mine stays below .05 volts even when revved. He had to go to work so I can't get the LTFT until tomorrow

The front sensor is not an O2 sensor, it is an AFR sensor. O2 sensors go from 0-1 volts. AFR ranges around 2.3-2.5volts but that is not what the computer reads, the computer reads how much current it has to supply the AFR sensor to keep the output in the proper band. Reading AFR voltage is beyond useless, and at .05 volts, was it even connected to the ECU when the voltage was read? or was that what obd2 said?

So, to make it short, you must read from obd2 the actual afr and see what it is doing to find out if the AFR sensor is broke. Also the rear o2 sensor can make the car run rich in cruise.

Hope that helps.

His numbers are for a narrowband sensor like the rear... 0-1V

Like Harlan said...the front sensor is a WB sensor that reads current

Oh, if that's your rear o2 sensor then you should have a CEL and be running around super rich everywhere.

Ok thanks everybody. My buddy apparently apparently doesn't know as much as he thinks! Thanks a ton for all the input, it helps a lot. I'll get all that checked tomorrow and get back to you. Harlan, those voltages were pulled from an OBD2 computer, not from the ECU. I don't have a code for my rear 02 so it should be fine...but it wouldn't be causing my performance issues anyway. He probably just read the wrong thing lol. There's definitely something amiss here, my mileage has dropped from 17-18 (when I got it in sep.) to 13-14

The OBD2 parameter is probably something else and mislabeled. Check your LTFT during cruise, that will tell us much more about what is going on.

And just too try and add a bit more to the mix ... the following is the Poor Fuel Economy troubleshooting procedure from the workshop manual

Attachment 228175

Attachment 228176

Attachment 228177

Attachment 228178

Thanks for that manual entry, it helps a lot. Just to reiterate what I said earlier, whatever is causing my fuel mileage is also causing loss of power at random points in the power band above 5k, which bothers me more than my mileage (I didn't buy the car because it was efficient HA) but the poor mpg is just further proof something is wrong. I'm hoping it is the AFR just to be done trying to figure this out, as it's been getting worse since October. I'll get all the requested information later today and and post it here.

Thanks again everybody!

Just put two and two together. Fix your thermostat first, if the car doesn't come off warmup fuel enrichment it will run like crap and have very poor fuel economy. Ignore any other symptoms until that is fixed.

^^^^I didn't realize the OP was having t-stat issues.

Shop manual agrees with Harlan ;)

Possible cause of poor fuel economy as indicated by shop manual is a t-stat stuck open.

The thing is, it does eventually get to the half way mark, especially yesterday when it was ~60F outside. When does it come off of the warm up fuel enrichment? Seems to me that once it idles at 750rpm it would be off of it. If I'm correct in this, it would've gotten off the warm up fuel enrichment like it does any warm day yet it still had the power loss issues. I have ordered a thermostat though :)

I'll get the t-stat taken care of, but would the t-stat cause power loss? It has always had that problem since I got it, before the t-stat issues, so I'm pretty sure that's unrelated (but the fuel economy could be because of the thermostat, you guys are right)

This thread miight help you

https://www.rx8club.com/trouble-shoo...mptoms-241859/

I've read that one, his problem does sound like mine, but there wasn't a resolution, which seems to be common with a lot of threads here :/

Heading over to my buddy's now to plug the computer back up

It does help, thank you for your input. I do not have a cat though, so I don't have to worry about that. It didn't have one when I bought it (which I didn't know at the time :wallbash:. I have a thermostat on the way, so that will get done. My reasoning though was that if it comes off of the elevated idle that is used for warm up, then it should be off of the enrichment fuel cycle as well. I did a flush/fill yesterday and I think I may have unstuck the thermostat, because it warmed up much quicker and stayed right in the middle of the gauge all day. I will be replacing it regardless. I still haven't been able to get the LTFT because my buddy's shop was really busy all day (on a sunday??) and I felt guilty bothering him :(. I will update when I have it

Ok another thing I remembered we found was that it is pulling ignition timing. I'm not sure what the units were but it was -2 (something). Is that normal?

I don't know what temperature it has to get to, the table is not accessible through accessport and I have never laid eyes on it. Making assumptions with the stock engine management of this car is a mistake because not all of it makes sense and it's kinda just shoehorned for our engine. It might be the knock sensor that is pulling timing. The stock knock sensor is useless so you might want to just unbolt it and see if that helps. Maybe someone with more knowledge than me will chime in.

This is interesting.
Worth a shot.
What would happen if you unplugged it? CEL?

BTW don't know if you saw it Harlan but Oltmann thinks the Knock sensor does work that ECU is reading values, he also thinks the Rear O2 does impact the AFR.

Don't have time atm to look for those threads .. just an fyi

Personally I have no idea, I'm just putting it out there.

I'll go do it now and see what happens :fingersx: