Just got my car back from the dealer today to have the "recalls" performed, and I also told them that my 8 has trouble holding a steady idle after the engine is warm. This causes a choppy idle with alot of vibration through the whole car especially when theA/C is on.
This has been there for months, even before I installed a Sr high flow cat. The first few times I brought the car in specifically for the idle/vibration problem, 2 different dealers told me this was normal for an 8. Then after reading some posts on the good old rx8 club forum, I saw that some folks had broken motor mounts that caused the same problem. So I brought it to the dealer again and specifically told them about the mount problem and sure enough the passenger side mount was broken. Well after that was replaced the vibration came back. Motor mount is fine this time, but now they are telling me they measured the exhaust temp before and after my SR cat and there is a 250 degree difference! The tech is now saying that the o2 sensor is slowly being melted which is effecting the idle(by the way I found out today that a new O2 is $300).I put a message out to Sr and I am awaiting thier response, but has anyone run into anything like this? My 8 is idling like a 72 pinto running on 1 cylinder!!

 

What is a normal temperature difference across the CAT?

 

That's a good question, I asked the service guy and he said all the tech's allready left and he didn't know.
Anyone out there know?

 

I think their giving you a BS answer.

A heat difference doesn't mean anything, if anything, it means the hi-flow cat is COOLING your car more effectively.

Considering there is a sensor at the end of the header, I would say that the one after the cat is doing peachy in comparison.

 

The in Cat sensor is about $60...the wideband on the exaust manifold is the expensive one. The exaust temps shouldn't be much different unless you are altering the tuning. Why would the midpipe change the exaust temp a reat deal if the mixture and timing are the same??