Stock ECU Mileage Switch
 

Anyone know what the mileage switch in the ECU does?

It changes over at 20,000 miles according to page Z-36 of the 1993 FSM wiring diagram. What changes at 20,000 miles? I'm guessing it doesn't reset when you reset the ECU?

Just curious if anyone else noticed this...

It is also mentioned on page F-189, but with no explanation of what it does.

*edit*

Google wins again!

From TurboRX7.com:

"What does the "mileage switch" do?

The "mileage switch" is in effect for the first 20k miles on a new RX-7.
It has the same effect as the "power steering switch". It adds some RPM
to the base idle to help keep the engine from dying."

Makes sense since it shares the same pin out of the ECU with the power steering switch. Duh. :)

I just wished I needed to worry about something that was going to change at 20k miles.

On the FC, I know it slightly changed how the emissions system worked.

Dale

Does anyone know how much RPM is added to the base 850RPM?

Wow, old thread!

I wouldn't concern yourself with it. Idle should be 850 rpm regardless. The mileage switch doesn't seem to really do anything interesting, there are other things to worry about than that :).

Dale

The reason I ask is that I just got the engine rebuilt and tranny swapped to a manual and now there are issues running the car at 850rpm. Sometimes the engine stalls due to a/c or fan hits, but not all the time. Runs fine if idle is set at 1100rpm. Any ideas? It idled fine before the rebuild and swap.

It's definitely not going to be anything with the mileage switch. Start by pulling and cleaning the idle speed control valve, make sure it's not sticking. You might have to do some fine tuning on the throttle body, especially the idle adjust screw.

I'd probably post your relevant mods and problems in a different thread. Your problem has nothing to do with the mileage switch.

Dale

mileage switch mostly affects the secondary air system and the automatic transmission control