Andrew_Lx

Hi All, new to the forums and new RX-8 owner

Bought a RX-8 about a month back from a wholesale dealer. Was a good deal at the time, everything looked good, minus the TPMS light but that was without a doubt from the aftermarket rims (no sensors) but otherwise in good shape. Got approved from a loan and picked it up two days later, and about half way home the check engine light came on. Well they hadn't smogged it yet (found it odd they didn't do that first) plus warranty so it was their problem. Took it back, waited a week, and what they did, they stuck one of those oxygen spacers in there because they thought the aftermarket headers were causing the light. Well that didn't work, and talking to the mechanic, he didn't seem real sure where to go next (mostly worked on older cars I think). So I took it upon myself to fix it. I realize I could have just taken it back and got my money back but I felt challenged.

The only code is P2096 - Post Cat Target Fuel Trim is too Low (or something like that). I was especially disappointed by the lack of information on this code. So, I feel inclined to share.

Vehicle Information:
2005 Mazda RX-8
Manual Transmission
OBX Headers - (AVOID)
K&N Filter - (no comment)
Stock otherwise

I have the TSB for this code but nothing really comes up odd or out of spec. It seems that just randomly the rear oxygen sensor sends out a low voltage but switches and works fine otherwise. So the spacer didn't work, and after thinking it over, I realized that the spacer would lean the reading out because its restricting the flow. Code says the signal is too lean, so I pulled that thing out. I also noticed that the front oxygen sensor placement was weird. OBX has it welded to the rear rotor header tube. That means its not even getting signal from the front rotor... So I had a muffler shop weld a bung to the front side of the cat and moved the sensor. This seemed to help but did not solve the issue.

I then checked the resistance between the rear oxygen sensor and the PCM, which I'm not surprised it was zero ohms. I didn't bother with exhaust leaks because I figured the front oxygen sensor (now on the cat) would also show lean if I were leaking between the headers and the cat.

So I was kind of starting to wonder if I should just take it back, when randomly I decided to look at the air filter, which at the time I didn't know was a K&N filter... I pulled that out and replaced with a Wix Paper filter. I've heard of over oiling damaging MAF sensors, but I vaguely remember something about the oxygen sensors being affected as well. So I removed the rear oxygen sensor and using compressed air I cleaned it out. I took probably 3 minutes to get all the **** out. It looked clean from the out side, but there was a lot of black stuff coming out while I was spraying the air into it.

I put it all back together and wal-la... its been 3 days and 200+ miles and still no light. I came back later and cleaned out the MAF/IAT. Runs great now...

Diagnosis: I bet the previous owner bought a K&N filter, added oil to the already oiled filter and boom, problems. CARFAX said the last owner only had it for less than 10,000 miles and that it smogged 7,000 miles ago... So in that 7,000 miles he fucked it up and said this car sucks and sold it. Idiot...



So for anyone else that has this issue come up, heres my recommendation:

- First make sure you're up to date on Dealer ECU Flashes
- If this happens after a mod, switch back and see if it goes out
- If not, repair any other codes first
- Then ensure all sensors are clean and working (and are in the right location)
- After that, check for exhaust leaks between the oxygen sensors
- Still have issues then check resistance from rear oxygen sensor to ECU
- Then if everything else is good, possible ECU fault



The amount of people who have this problem with vehicles of all makes (not just mazdas) suggest its something simple, and a dirty sensor is just that simple especially with growing popularity of K&N filters...

Andrew

Cuban97

Hi i have a 2004 rx8 automatic with only 82120 miles i have good compression on both rotors i got new spark plugs, new wires, new ignition coils, new knock sensor a new throttle body and a nee maf sensor and now i have three codes i have a p2096 a p0171 and p0102 the car turns on and drives but it idles ruff and turns off. When is cold turns on a lot faster when it warms up it takes a couple of try's to turn on and i have to constantly press on the gas. Any one have any answers I don't know what to do anymore.

RX8Soldier

iTrader: (24)

when did you get the new parts for your car? Did you reset your fuel trims by unplugging the battery when you had this work performed?

Have a read through this thread https://www.rx8club.com/series-i-tec...m-lean-229663/. Hopefully it gives you more insight and troubleshooting methods. Come back and report what you have done.

Cuban97

Yes I unplugged the battery everything I replaced each part. I cleaned up the o2 sensors as well I don't know what is going on now.

RobsRotary

I seem to be running in to the same problem. I haven't swapped out my header but I'm running the TurboXS Hi-Flow Cat and cat back along with a K&N panel. I tried switching to a paper filter but it didn't resolve the issue. I reflashed the ECU with versa tune using their pre-built flash for my configuration yet it still keeps popping up. The downstream O2 was replaced when I did the cat so at this point I'm lost. Any ideas?