Codes and Issues after Maintenance Items
 

I'm at 90K miles and got started on some additional maintenance items. I have been doing the plugs and coils on a regular basis but decided to go to an aftermarket solution. I got the below codes after re-oiling my K&N air filter (I know, not much love for the filter on this forum) and changing my ignition coils to BennettBuilt Performance coils.

P0171 - System too lean
P0037 - O2 Sensor Voltage Low

I then replaced the MAF sensor and it appears to cause the P0171 code to go away and now it is back. I also replaced the battery.

I've been having lower miles per tank (only 250 instead of the 280 I normally see) and some power issues around 3K RPM.

Could this be an electrical issue or should I attempt replacing a few more parts?

Chances are you forgot to plug something back up properly and now have a vacuum leak, as you need to remove parts of the intake to get to the ignition components.

And hopefully you didn't overoil that K&N and that 1BHP is worth it.

Any solution to an overoiled filter?

Go back to stock paper filter is a good solution for me.

It's pretty hard to improve much upon the stock intake system of an RX-8. Like I said, the K&N drop-in filter gives you maybe one extra horsepower but also leaves you open to having oil on the MAF and even possibly sand ingestion problems.

The instruction on reoiling from the K&N site is also pretty vague to me. They don't really give you a quantitative measure, just "oil until it's red", which is easy to mess up.

But anyway, check for vacuum leaks first. The OBD2 codes pretty much spelled it out for you.

I replaced the MAF sensor and it worked for a while. And then stopped working I think it might be the overoiled filter. I did check for leaks and it seems not to be the issued.

I'm going to squeeze out the extra oil, clean the MAF sensor again. If that doesn't resolve the first code, then I will replace the filter to a paper one.

I wanted to replace the O2 sensor after the first code clears as I don't want the new O2 sensor to break.

Thanks for the input UnknownJinX.