S1 auto limp mode(no codes)
 

I bought my 2005 automatic rx8 about a year ago with a blown motor, and I just recently rebuilt it. It still starts and idles fine, and the first few drives it had good power up to the 4k wear in “redline”. It is now in a limp mode, limiting the commanded TAC to ~10%. The CEL comes on shortly after starting, but our innova 5210 doesn’t always pull any codes. Occasionally there is an evap or ESS code, but neither are consistent. My assumption is that the ESS code is due to battery drain. At idle: The long term fuel trim is 20% which we know is high. The intake air temp is 160F which definitely seems high. The MAF reads 6.4g/s which seems fine. The MAF was cleaned, and we’ve checked for vacuum leaks. We have also tried cleaning the OMP connectors. The spark plugs are new but coils are not. The car is stock other than a turboxs midpipe. I am trying to diagnose this problem without just throwing new parts at it. Any ideas?

I would try a different scan tool and see if a different one will pull more codes. My scan tool has two options scan and diagnose. A scan will not always pull up all current codes. Running the diagnostic portion of the scanner will allow me to do a full system health check and oull codes from each individual system. Each scanner works differently so you'll have to play with yours or try another.

Seems the most common reason for limp.mode is oil metering pump failure. Don't rule that out until you have run a compete scan.

The long term fuel trim is high at 20% but that could be from a number of things. Is it positive 20% or negative 20%?

Limp mode is either OMP, which is the most common or the drive by wire throttle system.
A lot of the scan tools will not display the OMP code,
get a more advanced scan tool and see if there’s a P16XX code (eg P1688).

Often the OMP does not throw a code if the position switch is not working correctly. It can get out of alignment and then not respond correctly and the car goes into limp mode

Its easy to tell if that's the case.

Remove the bellows for the intake... reset the ECU. See if the throttle reacts when the key is on and not running. If it does then start the car. If it works for about 8 sec normally and then stops reacting it's in limp mode.

Usually any drive by wire errors will throw an immediate code and you can assume that the problem is the OMP. The only other error could be the coolant temp sensor but it's easy with any scanner to see if it's working

Thanks for all the suggestions. We tested all the wiring for the OMP stepper and OMP position switch and it’s all fine. We tried tons of different positions for the position sensor and nothing changed. We pulled it off and tested it with a multimeter and it always reads open circuit. Does this mean it’s a bad sensor? If so where can I get one?

Unfortunately you can't buy the sensor itself. You have to buy the whole Omp.