New build hard starting, idles ok then runs away
So I rebuilt a LQ4 with LS3 heads and intake with a BBK 100mm Cable TB and ASA Cam. The motor has a hard time starting unless I crack the throttle blades abit (TPS voltage reads 0.71v). Once its started it gets into a good idle but sets the IAC position to 0. After a while, it starts running away and increasing the idle RPMs.
What should i be looking at to fix the starting problem? i know i need to dial back the throttle blades a bit. Do i need more or less starting timing/Fuel?
Sounds to me like the hard start and the running away both have to do with the IAC. If the blade is all the way shut when cranking , the motor might not have enough air to start unless you press the throttle, but it's still enough for idle. There are IAC settings in the tune but it kind of sounds like the IAC valve isn't hooked up right or installed properly. Just my best logical guess , I've only dealt with DBW stuff.
2001 Z06 : 856/830 : Built LQ9 403ci : D1SC 17psi : Self-built , self-tuned.
Well originally that's what I thought, I did some wire testing to make sure I had the correct pinouts and I did. I think that its the startup variables that need to be adjusted because the idle will command less air over time and the IAC trys by closing. once its closed the idle will slowly run away because the throttle blades are still cracked and its getting more air than it need at idle. I cant close the blades though because i cant start the car any more. so i think the starting/cranking is where i need to look at.
Did you have to install the iac valve yourself on the bbk tb? Is it possible to put it in backwards or something? As far as the tune, you have control over IAC count , idle airflow, startup airflow, cranking fuel, cranking spark ... I'd start with the IAC table and experiment. Hopefully someone more familiar with dbc will chime in
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