2000 alero v6+manual swap IAC counts decay/idle RPM drops-Only between 20 & 1 MPH

Hello all. (3500 lx9/6speed f40) Engine RPM is being commanded well below the 950rpm set-point whenever VSS is between 20mph and 1 mph. If VSS is above 20mph or at 0mph the 950rpm target is hit @ 43-45 IAC counts with no issues but between 20mph-1mph IAC starts to decay slowly from the mid-forties to as low as 23 counts and the idle rpm drops along with it. Disconnected the IAC @ 950rpm and the car drives/idles normally. Disconnected the VSS and the car drives/idles normally. Going to try to jumper the pins on the disconnected auto trans connectors to simulate neutral next but beyond that I don't know what to try. The VCM is from an automatic transmission equipped car so maybe something is going on there behind the scenes? As far as I can tell, HPtuners allows only for base idle adjustment on this VCM (No throttle cracker/follower adjustment ect...). Any feedback would be greatly appreciated!

Tune and log.

Okay

Why is idle set so high?

Experiment to reduce transmission noise when idling in neutral with clutch engaged. OEM dual mass flywheels are no longer available to help with that.

Jumped auto trans TFP and Range Switch circuits to set the park/neutral flag in VCM data list to no avail. Looks like VCM is trying to force idle speed/iac counts down to 650-ish rpm between 20mph and 1mph and this engine just will not idle that low consistently (Heads/cam/intake mods). Maybe a transmission segment swap from a manual trans equipped car might help? No v6 cars came equipped with a manual, so that might be an issue. The HPtuners commanded base idle set-point gets ignored every time VSS is between 20mph-1mph without fail. I have no idea what is causing the override so far

What is the operating system? You need a XDF file so you can define the tables you are looking for in HP Tuners. These XDF tables are for a 2003 Malibu 3.1 V6.

Attachment 154635

Thanks for the info Maple Leaf. 12201467 is the operating system. How did you pull that xdf. file from your Malibu?

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Originally Posted by dbrals

Thanks for the info Maple Leaf. 12201467 is the operating system. How did you pull that xdf. file from your Malibu?

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No problem, your operating system is in the XDF files I have. You should be able to add those tables you need to fix you low idle issue.

You can pull the XDF files from tiny tuner for GM V6 engine vehicles using the P04 as long as your OS is defined in tiny tuner. Follow this thread to understand and be able to define tables that you need.

Beginners Guide to User Defined Parameters using Tiny Tuners Database

Perfect. Going to give that a try.

I would also add in these 2 as well for the camshaft as you said was changed/upgraded. You can use a cam calculator online to confirm proper injection timing.

Injector pulse boundary (Fuel injection delivery boundary as number of reference periods after TDC)

End of injection pulse vs Coolant (The end of injection target measured in reference periods after the injection boundary that the normal injection pulse should finish)

Whoa, never thought about that side of things and did not know that injection timing/boundaries and what-not could be modified on our PCMs. Kinda peeked down that rabbit hole to see what is up.... Cam is not too radical. .556/.560 valve lift (w/ 1.6 rockers) 222/226 duration at .050 106 intake center 110 LSA