Need a bigger IAC Valve...

[Atomic]

I have been fighting this issue ever since I put in a new cam. Specs are: LS 402, ported L92 heads, 230/233 114+4 cam, bw s482 turbo, holley hiram intake, nw 92mm cable tb, 2002 pcm.

Trouble is it seems as if the IAC isnt big enough to cover the whole range of engine operating conditions. For instance, if I have the blade screw opened up enough so I dont have to give it pedal to start, it will not idle down (IACP=0) and pulls timing in an effort to reduce engine speed. If I close the blade enough where it has control when hot (IACP>0), I have to give it roughly 10% throttle for the first few seconds to keep it running.

Any suggestions? This is very frustrating.

[Atomic]

No thoughts eh...

[maxg1989]

Have you tried to reset your IAC and TPS?

[Ben Charles]

IAC position can be controlled by fuel or spark. You can make it read 0 when spark is high or when its rich. Play with the VCM controls and setup the OFLA table correctly.

[DSteck]

I run into this fairly often with vehicles that max IAC counts when cold, and you can't do anything about it. Frustrating as hell. I only seem to run into this with aftermarket throttle bodies though. It's like they don't size the IAC appropriately.

[Ben Charles]

I think most aftermarket companies kinda of skimp out on the IAC design b/c they don't realize the importance.

[Atomic]

Are there any aftermarket IACs or any option to improve a factory one an aftermarket tb? What do you do to bandaid this? When it pulls timing if I leave it ideling for any length of time the underhood temps get ridiculous because of the turbo.

[Ben Charles]

You and pull the TB and open the IAC passage some, that will help.

[Atomic]

Might give that a wack, may as well. To answer your earlier question the TPS sensor has been replaced....although strangely at idle it will sometimes read 0.39% instead of 0, not sure if this is an issue or not.

Its annoying HPT can only command up to 127 steps in the scanner, not the full 310.

This TB and IAC worked fine with my last cam, which was less aggressive (226/226 117).

[LSXstang94]

drill a small hole in the blade of the throttle body so it gets more air but the TPS still sees 0, not sure it its the fix in this particular situation but it works in some

[Atomic]

There is already a 1/4" hole drilled in the blade.

[acehaag]

If your not getting enough air flow through the whole iac range would it be a possibility to shim it iac out of the throttle body a bit to increase the air flow through the whole range? I'm just throwing this out there because I like to think outside the box.

[Atomic]

I think that would do the same thing as adjusting the blade screw....I need a longer travel for the valve I suppose.