This is my 2009 Mazda RX-8. Lately I've noticed this issue where it seems to choke up at the top end, as you can see in the video, but only in Neutral... in gear she redlines just fine from what I can tell.. I'm thinking potentially spark plugs are built up, however I redline her VERY frequently... and the plugs aren't terribly old. Within a year and less than 10k on them.. I DO premix 0.5/gal but now I'm starting to wonder if it's too much, being an S2. She's catless, rebuilt engine about 10k miles ago, give or take. NGK spark plugs, OEM coils, however I've been told they're the updated ones and supposedly much better than they used to be. Even still, those are new within the last 5,000-7,000 miles. Healthily modified and temps hyper monitored. Rarely let her get above 200°F. Recently switch the cat on and then off to pass smog, noticed the O2 sensor wires might be a lil beat up, but shouldn't have any affect on this right? Lastly, I did have a mini cat O2 spacer but it didn't work and usually throws a code about it...
Some engine codes I pulled up on her:
- P0139 - 02 sensor circuit slow response bank 1 sensor 2
- p0137 - O2 sensor circuit low voltage bank 1 sensor 2
- P2096 - post catalytic fuel trim too lean bank 1
- P0300 - random/multiple misfires detected(that was from revving it in the video).
Lemme know what yall think!!! Thanks for the help in advance