LS1 High RPM on Start up

[waldoffs]

Hey guys i have tried to change a heap of settings to stop the motor from revving so high on initial startup. So when i start the ls1 up it instantly hits about 2000rpm then drops back down to about 1000rpm until its got a bit of warmth in it then lowers to its 650rpm. Im just trying to stop the instant 2000rpm hit it has on start up. Ill include my tune file if someone could take a look at it and advise me what to change. Mods are LSXRT truck intake, 92mm tb, headers and 2.25inch twins and 2 cats. Runs a 4l80e

Stock Clubsport Engine but with 4l80 trans decem 27.hpt

[RDF1]

How about a datalog?
What throttle body is that and what are the IAC steps at hot idle?

[waldoffs]

I will have to record a datalog and upload. The throttle body is a FAST 92mm. IAC hot idle says 0 on vcm scanner. Its not the idle thats the issue..idle is fine hot or cold. its just the initial fire up of the motor. i tried adjusting the start up flare but had no affect.

[blindsquirrel]

If hot idle is showing zero IAC counts then idle is NOT fine. You do realize the IAC is what controls engine speed any time the throttle is closed, like when you are getting your startup surge/flare, right?

[waldoffs]

Sorry the scanner was only logging IAC desired position and reading 0 at warm idle. I will have to add the channel in to see actual IAC step

[RDF1]

I will have to record a datalog and upload. The throttle body is a FAST 92mm. IAC hot idle says 0 on vcm scanner. Its not the idle thats the issue..idle is fine hot or cold. its just the initial fire up of the motor. i tried adjusting the start up flare but had no affect.

Theres reason why i asked what the IAC position was.
see what it is when its hot. IF Desired position is 0 and actual position is 0 then what does that tell you? Means throttle body is open too far and its getting too much airflow.
Thats a possible reason for startup flare.

[HATEHPTUNERS]

Also, on your log add channels for timing advance. What the PCM is doing with timing could help you drill down on what tables need adjusting in the tune. If the PCM is pulling timing, then you have too much AIR from some where and the PCM is pulling timing to control the idle. Likewise, if the PCM is adding timing.. it could mean there are fueling issues and the PCM is adding timing trying to prevent a stall. Also look at your IAC PARK POSITION airflow table.. The numbers in those cells is where the IAC will be when you first start the engine.. You already said that the IAC counts at a hot idle are ZERO... so, if the IAC is at 10, or 8, or anywhere close to that as dictated by your IAC PARK position.. then on first start-with a 92MM TB you are going to have a high idle until the PCM closes the IAC and takes that excess air away. Next question.. Have you adjusted your IAC Steps Vs. Effective area? Here's a video that can help you with that; https://www.youtube.com/watch?v=621bcy3Epzo larger TB's typically require updating the parameters in the tune so the PCM knows how large the TB area is.

The other thing I notice is that your IN PARK idle spark is in the 14's... Your in gear is just a smidge higher.. Those tables can run a bit more spark than that.. and if you have a performance cam you can run a LOT more than that. I'm guessing a good log with the right channels in it will help drill down on the problem.