hi, had my rx8 (2003 base model auto) for 5 years, and it has been faultless- no hot starts etc. Suddenly it now takes forever to start, churns and churns and eventually fires up. As soon as it catches the revs rise to 8000rpm, the only way to save the engine is to stick it in gear, with the brakes on as it is like a caged tiger! its had new coils and ht leads and a svc recently but there must be a simple solution- it has just happened overnight. Any help please? thx

 

It goes to 8000rpm? It sounds like you have a huge vacuum leak orthe throttle is stuck open. Take the intake tract apart and start troubleshooting?

Don't hold the brake with the engine going 8000rpm, you'll destroy more than the engine.

 

Any codes, CELs? Probably Drive by Wire failure, stuck open throttle body.
Remove your intake to see throttle body action, if it is closed then you have a huge vac leak after the TB.
If your TB is wide open when you are not pressing the pedal, try to move TB plate with a pry bar or something to see if it is stuck, or ir can be DWB failure.

Since you are an auto, I highly suggest do not slam it in gear at 8000rpm, the "band' thing in the trans will be damaged, your torque converter will overheat, your drivetrain will take a lot of that shock.

 

thankyou @Loki, will have a look at the vacuum leak and the throttle. the throttle works fine when feathering it to get it to start, so maybe the leak is a good place to start. thx

 

thankyou for your advice @Shaozhou Zhang, will check for error codes and investigate the throttle body.