I have a bit of a strange issue.
Background: I have a cable driven standard throttle LS1 with a cam and M6. It feels like I am struggling to get enough air into the motor when starting cold. It will start with a little bit of throttle input and idle fine after that. Driving around is no issue (no stalling at lights etc) and the VE table is very close at idle (when warm. When cold the wideband reads leaner than commanded). When hot the IAC steps are 30ish (They drop down to 30 from 200 in the last 10 degrees C of the warm up. Cold idle RPM 900, warm 800. The engine runs really well other than needed to feed it pedal to start it and keep it running for the first 20 off seconds. Opening up the throttle blade ends up running out of IAC step when warm.
The strange issue: When cold and before starting, if I use the bi-direction controls to drive the IAC to 0, then turn off the controls so it looks after itself, it starts and revs stupidly high like the RAF is way too high. It will pull a heap of idle air and then idle at 90 IAC steps (when cold)
If I do not play with the IAC via the controls and attempt to start as per normal use, it is short of air. It will idle cold at high 200 steps and the desired idle air flow numbers are a lot higher (26g/s compared to arounnd 9)
Two data logs attached. First one is driving the IAC to 0 before starting, second one is starting normally straight after. You can see the desired idle air is hugely different. Tune attached also. RAF numbers in the tune is what it calls for when starting from cold (Russ K style)
Its almost like the IAC doesnt know where it is unless I use the controls to drive it home first. In normal use it feels like it needs to open more (even though the desired and actual positions are calling for 300 odd steps)
Is there a way to make the IAC drive closed before starting by itself? It feels like mechanically there CAN be enough air, but for some reason its not happening.
Update: Looks like the IAC might not be physically opening all the way. I removed it when the IAC counts were at 310, unplugged and could wind the pintle further in. Re-installed it in the fully open position and it started and idled at 2300rpm then pulled steps out and the IAC and idle operated as it normally does after 30 secs of running. Showed me that the IAC / throttle blade can flow enough air for a cold start, but for some reason the IAC isnt going where it should.
Switching off and then starting again put me back at square 1 (IAC not opening far enough).
The IAC desired and IAC actual PIDs matched, but in reality the IAC was not physically reflecting this. For some reason, the IAC will not open all the way unless it is manuall driven there by hand or by the HP tuners controls.
Swapped for an alternate IAC and it seems to be much better. Now to start again with the idle tuning and see where I end up.
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