IAV (idle air valve) question.

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Pinger

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Does anyone know if the IAV is utilised for anything other than idle speed control? Specifically, I'm trying to find out if it is opened during over-run conditions. Question relates to a 1999 Vortec 350. TIA.
 

JayMB

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The IAC also bumps up the idle when the A/C comes on.

On LS 0411 stuff, the IAC does this thing called "throttle follower" where it helps to stop the engine from stalling whenever it is suddenly unloaded. Had to mess with that stuff a bunch to keep something with a large cam running. Haven't looked too closely at any tunes from a black box myself.

If you're troubleshooting and it's moving/opening while coasting that might be intentional behavior.
 

Pinger

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If you're troubleshooting and it's moving/opening while coasting that might be intentional behavior.

That's the bit I'm trying to figure!
Possibly it opens to reduce severity of engine braking? Or for air to the cats? Or another reason?
Don't really care what the reason might be - only if it does it!
 
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