Cannot change idle speed on E38 PCM

[njedwardz]

Hey all,

I'm working on the idle tuning on my 2013 Corvette A6 that I've recently had a cam put into. The idle is pretty much perfect now but it's idling a little high for me. The issue is, no matter what idle speed I command in the tune, the PID "GM.idlerpm" (which is "desired idle speed") remains at 896 (which is its version of 900 RPM). I CAN go into the DVT tools and command it lower, but obviously this isn't a real solution.

To be clear, the issue isn't that I have too much airflow and the car won't hit the commanded speed; it's that the car is not commanding the same idle speed that I am...For example, whether I set the commanded idle RPM to 900, 875, 850, 700, etc. the PCM will not command anything lower than 896 unless I manually force it do do so through DVT. Commanding higher values DOES work as my idle speed after start table IS working as programmed until it reaches any number below 900.

This is a new issue - idle was fine at ~600 RPM before the cam.

Anyone ever experienced a similar issue? Solutions? Tune file is attached. Will try to record/upload a datalog of what's going on as well when I have a minute.

I'd appreciate any help! Thanks in advance!