dstac44

My rx8 has been having issues recently and I parked it in the garage fearing I would cause more damage. It just seems like it hits a wall once getting above 5k, it wont rev any further and it feels as if the engine is going to blow if I don't ease off the throttle. The car has 175k miles on the original motor.

I have been scrolling forums for weeks and have a couple ideas of what may be wrong:

Ignition system, clogged catalytic converter, SSV valve, or low compression,

any potential other problems you can bring to my attention would be greatly appreciated. If you have a suggestion of what to start with that'll help me a lot. I'm trying to avoid sending it into defined autoworks or a mazda dealership for diagnosis and repair, I'd like to do it myself for the knowledge and saved money.

Finally, I would have posted this in the "series 2 technical troubleshooting forum" however It says I do not have permission to, as I just joined rx8club.com

Loki

iTrader: (1)

SSV opens at 3500 so if it was that, you would start to feel power loss before 5500. Any OBD codes?
The secondary fuel injectors open around there, that would be another thing to eliminate.

Do you have a way to log data? If your AFR drops when it gets to 5500, that would confirm fuel injector issues. If AFR is good but the car isn't accelerating, I'd blame air (valves, cat, etc).

Does the car have any modifications?
What does "feels like engine is going to blow" mean?

dstac44

The car is 100% stock besides the removed mufflers.
by "feels like its going to blow" it just scares me when it hits the "wall" at 5.5k, I'm always paranoid driving the car, I feel the days are numbered on the engine since it's such high mileage
I also do not have a way to log data my friends have code readers but I'm not sure of the quality of them, I know some readers only will pickup certain things
Finally, the only code I've ever got from the car is the o2 sensor. The engine light turns on and off but for the past few months it's remained on so maybe there is something else.

Tamas

iTrader: (1)

First thing you should do is reading the OBD code(s) to find out what the CEL means.

zoom44

go to any auto parts store and they will usually read the codes for you for free or lend you the code reader for free by leaving your license or something so you can go out and read them yourself. seriously it sounds like clogged cat to me and if your codes come back o2 sensor related that where you start.

Loki

iTrader: (1)

Yeah definitely get the code read Driving around with a check engine light isn't great for the longevity of any car.

dstac44

Okay I'm going to get it scanned at advanced auto parts, I just drove it today and it the EML flashed after hitting the "wall" at 5.5k rpm, me and my friend who also owns an Rx8 are both 99% sure it's a misfire but do not want to dump $400 on BHR coils without being certain.

dstac44

UPDATE
I went and got the codes read,
P0420: catalyst system efficiency below threshold (bank 1) secondary DTCs
P0411: secondary air injection incorrect upstream flow detected
P0139: O2 circuit slow response (bank 1, sensor 2)
P0300: random misfire detected

Will removing the cat solve my issue? that is what I would prefer to do and replace it with a straight pipe.
For the misfire I'm assuming I need to go ahead and replace my coils with the better BHR coils. however the person at autozone told me the o2 sensor could be causing misfires. Should I replace the o2 sensor or is removal an option?

Loki

iTrader: (1)

It sounds like your cat is clogged, I'd have it taken down to examine and replace if necessary. You can worry about coils later or if they're old, may as well plan to replace. But they're not your main problem right now .
Some AutoZone people are smart, but safe to assume they don't know RX8s, get the cat fixed then if the codes still come back troubleshoot further. Do not drive except to the shop until the cat is fixed or confirmed good and keep the revs low.