Idle Air Control Valve quick ?

[gregory_gdp]

I have a 91 3.1L Lumina sedan and I've been having some issues with rough idle, stalling and a really nice vibration that goes with a loss of power. Seems like it's only running on 5 cylinders I've checked and replaced the spark plugs and they are working. I also checked for Vacuum leaks (didn't find any broken lines). I remember I had the same problem some years go and the cause was a IAC Valve that went bad. Last time it did that it threw a CEL which it's not doing at the moment.

My quick question is after taking the Intake assembly apart and cleaning it up I was looking at the IAC Valve and I was thinking that the Valve is supposed to be closed when not operating but for the life of me I'm not sure and was wondering if any one could answer that simple question. Currently it's not closed.

[maxwedge]

The iac cannot cause a misfire or loss of power, it merely controls idle speed, keep looking for the root problem.