I searched w/o success. My question: I have edited my original question to be clearer: why are the "AC on" desired idle RPM values a set value while the other desired idle tables are coolant temperature based? If the engine is cold and the AC is on, what table does the ECU use? This is not so much a tuning question, but a general eduction question about how the ECU works.

 

Desired idle speed is just that Desired engine speed.. The other tables are stepper values of how much the IACV should be open at that particular engine speed (and particular load) as load will vary based on what accessories are on.. Sometimes its not enough to compensate for increased load with the A/C on, you have to increase alter idle speed a bit too.

coolant temp (Engine temp) will obviously have an impact on idle quality, as a cold engine prevents adequate fuel atomization and there fore the "Choke" (old school carb term) increases fuel into the engine, and Idle.. The combination of these tables functions in a similar manner..

This of course is independent of "cold start" and "Cranking" settings as there are different tables for that (Not all of which are currently known)

 

I find the idle Stepper look-up table to be confusing. The Desired ISCV tables make sense but the look-up table has TPS on the x-axis and rpm from 0-1016 on the y-axis. Makes zero sense. Also none of the values on the stock 05 ROM are different going across the x-axis. Are the table definitions in ECUflash wrong?

 

Yes, the table is wrong in ECUFlash. The axes are coolant temp and load. This has been discussed in one of the big threads floating around.

Actually, there is a mini discussion going on about it in another thread started about the throttle hang.

 

Wow forgot about that..

 

But why are the stock 05 values the same going across the x-axis? That means coolant temp really doesn't matter and only load matters in the look-up table.