Idle desired rpm random lowering

[Baezi z06]

Hi i?m tuning a 1999 firebird with Gen 3 PCM and having problems tuning the idle, but i found out why, desired rpms drops down to very strange numbers like 187rpms , 258rpms 457rpms , but sometimes back to normal., i can?t find out why the pcm is comanding this...
but if i set the rpms in the scanner while logging it sets and stays, and offcourse idles.

attached is the file

thanks Baering
HP Tuner Iceland

[Baezi z06]

here is a log whatch idle desired RPM

[Turbo_Mike]

You're in luck, I've had this happen before.
The way that you set up the trans is incorrect. Either you have incorrect data, a bad segment swap, or the wrong PRNDL setting. But the problem is from the trans settings.

-Mike

[Black LS1 T/A]

This is an interesting response.

Can you say what the PRNDL setting should be? Stock? Or some changed value based on build?

[Turbo_Mike]

This is an interesting response.

Can you say what the PRNDL setting should be? Stock? Or some changed value based on build?

I dont recall, it happebed to me on a LS 24x cable throttle with a 4L80 swap. It was some wierd combination of when you set the transmission box to 4L80 without a the correct segment swap and dont update the PRNDL value. I ended up starting over with a non swapped file and worked at it until I found a combination the both shifted and idled, but it was some time ago. It was very frustrating, but it ended up being something in the trans side that caused the idle problem.