I noticed today while driving my RX-8 that if I come to a stop, take my foot off of the brake pedal, and let the car idle for 10-15 seconds that the brake pedal becomes rather firm. It's not as firm as when you push the brakes when a car is off, but it's definitely more firm than normal. When this happens if I put my foot back down on the brake the idle will raise a slight amount and the pedal returns to normal. If I let it idle for another 10-15 seconds with my foot off the brake it will firm back up. I don't recall my last RX-8 doing this. Is this normal?

Sorry in advance if this has already been discussed. The only search results I could bring up were soft pedal threads, not firm ones.

 

I guess that means no one is having it. Great.

My guess is it's vacuum related but the car runs perfectly, I have no problems with my brakes outside of when at idle, and I'm CEL-free. From the threads I've searched it appears people report CEL's when the car has a vacuum leak.

I have a K&N intake which requires the replacement of a hose (that connects a cannister to a vacuum check valve from what I can see) that helps to operate the last port that opens up after 7000rpm. I bought the intake used and it didn't come with the hose, so I bought a replacement at AutoZone but it was slightly too big. I clamped each end off as best I could but I suppose there could still be a leak there.

 

its more than likely normal. as your brake booster takes vaccum from the engine. and when you press the brakes at idle that vaccum is used. so the idle is raised to compensate for the loss of vaccum at the booster...