Alright guys so im having trouble with my 2004 rx8. When its at idle the rpm's seem to be low and the car shudders. My father used to be a car mechanic for years but has never worked on a rotary engine so he has provided some insight to a degree. He told me that had the car had a normal engine he would of guessed it would have been the valves, but this car doesn't have any. We changed the spark plugs, the coils i even checked the throttle body. I ran the car through through our computer tester a while back and it said something about an "error with the control module". I don't believe its the engine mounts. Any insight you guys could provide me with would be great.'

thanks

 

Check and clean the MAF and the ESS(Eccestric Shaft Position Sensor), are there any CEL? Since you have a 2004, I wouldn't rule out the engine mount(s).

Mazda TSB of testing the motor mounts:
- On manual transmission vehicles, when decelerating in 3rd gear with engine speed less than 3,000 RPM at approximately 30 MPH (50km/h), then quickly depressing the accelerator pedal again, a hesitation may occur. This symptom can only be observed in this engine speed and vehicle speed range.