I have a 05 six speed RX-8 that has 11,000 miles on it. Every now and then, I'll be on the freeway and I'll hear a faint knocking sound. Sounds close to leaves getting caught in a fan. Seconds later my car will stop accelerating and when I try to shift down it has no more pull than in the higher gear. I shift up and down a couple of times and it will go away. Doesn't happen everytime I'm on the freeway, nor does it happen even every week.

I have no idea what's going on, any suggestions??

 

Take it to the dealer.

 

that should be covered under warranty assuming your transmission is stock and no upgrades (to transmission/drivetrain) have void the warranty.

 

Sounds like engine might be having a pre-ignition or pinging problem. Pinging in a rotary engine does not sound at all like in a piston engine If the engine computer gets a ping signal from the knock sensor it will retard spark timing quite a bit on the 8 and kill your power. Are you using 91 or better Octane fuel or cheating with the cheap stuff?

 

I always used 91 octane or better since purchasing the car, but do you think maybe condensation has built up in the tank diluting the fuel? I say this only because at times I've waited until the light came on before filling up. Could a simple dose of that fuel cleaner do the trick?

thanks.

 

Running the tank untill low should not cause you any problems. It would certainly not hurt to pour in a bottle of fuel drier and maybe a cleaner additive to see if it helps. Will be kind of hard to know if it is working if problem only occurs once and a great while. If possible it would be a good idea to try and keep a tab on when the noise and power loss occurs. At a certain tank level or after filling tank from a certain gas station. How much throttle you were giving it at the time. Uphill/downhill etc. If you are able to do this will be much easier for you if you take in to the dealership and you are able to make the event happen on a test drive with them. Otherwise you will probably only get the old "Unable to duplicate and NO problem found". Do not remember seeing anything about updated PCM calibrations for pinging on an 8.
There is a Recall #4206F coming out soon for the RX-8 that you should be getting in the mail before too long. I believe that mailing should start going out tomorrow. There is a PCM calibration update that will address some over oil metering problems that may be contributing to what you are experiencing. Variety of other things get done as well. You should be asked when you bring the car in if you have been experiencing any severe power loss or low idle problems. That would be a great time to bring this up to your dealer and get it on record. Might even be a better idea to call and get an apointment to look at this power loss problem before the Recall comes out. That way the dealer cannot say you are only complaining of power loss because of the new recall if you know what I mean.