If the CEL is flashing, that means stop driving it.
What is the specific code for the O2 sensor?

Definitely check your plugs but you may also need new ignition coils. If it has been misfiring for a while, you may have damaged your catalytic converter so have that checked out, as well. A bad cat can clog up the exhaust and cause a heat to build up near the exhaust ports. This will cause a coolant seal failure which will require an engine rebuild.

 

 

If you're uncertain about the age of the ignition coils or they're older than 30k miles, replace them. This is not a joke. Failing to do so kills engines.

Since you also have a cat code, have the cat removed and inspected visually inside. If the catalyst has broken, it will also kill your engine.

If the plugs look bad, definitely replace them, but not at the dealer. They'll charge you way to much. Go to a NAPA or similar store and get spark plugs, wires and coils for much cheaper.

 

 

Information that should have been included in your first post...

 

 

 

How old is the gas? Is it 4 years old as well?

That could be a factor as well.

 

 

To be honest, I don't think the spark plugs are particularly difficult to change. Any mechanics should be able to do it, really. If anything, the spark plugs are easier to do than on a BRZ or WRX(good luck with those flat 4 plugs)... Same with coils and wires.

Just make sure you put in the right spark plugs(leading and trailing) and connect the wires correctly.

Depending on where you live, it may help to start investing your own tool set. More initial investment, but less money in a long run.

 

 

From what I have read misfire = plugs coils plug wires changed and check cat.
https://www.rx8club.com/new-member-forum-197/rx-8-symptoms-causes-249529/

 

 

Could also be ESS sensor, ESS tone wheel or ESS profile.

 

The coils should be replaced when you replace the plugs and wires. These really go together on this car. Keep us updated on what happens after the dealer replaces the coils as it sounds as though the dealer is doing the work.

 

 

If it failed where it is reading rich and you drive. You will end up with it running leaner and leaner. Lean conditions are not good to our engine's. All it takes is one good detonation event and you have to have a rebuild. The up stream o2 sensor is the more expensive of the 2.
can you get the cel codes and post them. A lot of good people on the forums. Just find out what codes you are getting and post them up. You can also look up the codes. Dont let a mechanic give you any end that cost you unnecessarily.

 

 

How did you determine that's the problem? It sounds... unlikely.

 

 

It would help if you could share the actual codes the computer is showing. There are multiple O2 sensor codes (the "fuel ratio" sensor is just an O2 sensor). O2 problems don't usually show up as misfires.

There is a difference between "has spark" and "has good spark"

 

 

I couldn't find the thread. A member of the forums did go through and test disconnecting the o2 sensors and maf. It would throw codes but the consensus was that the default closed loop was good enough to let the car run with out major problems. I would definitely find another shop. I would fallow loki's points to check also. (Check the ecentric shaft sensor and trigger wheel). Best of luck.

 

An air fuel ration sensor is an EXTREMELY unlikely culprit. There would be a stored code indicating that it was reading incorrectly and the tech would have to look at the live date and freeze frame date to help determine what exactly what was happening when the code was stored. Fuel trims would be a little wonky with a bad AF sensor, but I've never seen a bad AF sensor cause a misfire. Did he ohm the AF sensor to determine if it was faulty? Did he check the wiring from the AF sensor to the ECU and was the ECU tested? These are all things to consider when diagnosing a faulty AF or O2 sensor.

Remember, a coil can pass a resistance check and still be faulty. Replace the coils.