Misfire at high RPM. Please Help.
 

Hi, I bought a 2005 RX 8 at the beginning of summer. Love the car. Within a week of ownership it started to flood and misfire. Searching the forums, I decided to replace coils and plugs. It was like a totally different car. It ran great for about 3 months. Now its doing the same thing with a new twist: it misfires mostly at high RPM's (above 6000). I've cleaned the MAF, Decarbed the engine, cleaned the air filter and reset the ECU. It throws the misfire code and also the code for the rear 02 sensor. I drove the piss out of it and crawled underneath to check for a glowing cat but no dice. It just rolled over 90,000 miles. Any suggestions?

Did you change the spark plug wires when you changed the coils and plugs?

I did not change the plug wires, but sounds like a good job for today.

Where is the access to check the fuel pressure?

Misfire and rear O2? Sounds like a clogged cat--even if you didn't see the O2 bung glowing.

Garage it . Pull the midpipe off and shine a flashlight down the honeycomb to confirm. Relatively easy procedure, minus the possibility of rusted exhaust flanges. I would recommend it ASAP--clogged cats are known to cause fires.

a good idea when this happens is to might as well upgrade to the BHR ignition Kit. that's what i did and it fixed the issue...

Visually inspect the cat to see if it's intact.

Definitely get new wires, and I would say clean your ESS sensor, also perform the 20 brake stomp reset, along with a ECU reset (unplugging battery for a couple mins.

I've had a suspicion that the cat has been going bad. So tonight after reading your post I ran the piss out of it again. It took me a min for my eyes to adjust but I could just see the glow through the o2 bung. Thanks for the heads up. It came in good time, I was just about to put it up for winter. Looks like I'm getting a BHR midpipe.

Thanks everyone, I'm glad I finally got this figured out.

Glad you found the culprit. On top of the midpipe from BHR, I highly recommend getting their ignition system (and new plugs at the same time), as running with a bad cat can have very harmful effects on the plugs themselves.

Hell, when mine went I had to replace all my plugs and coils...

I just want to say that a glowing o2 sensor on the cat doesn't mean that it's clogged. It's quite common for the o2 sensor to glow orange in a perfect ring and it working just fine and is perfectly intact. You need to visually inspect the cat to be sure.