Idle Air Control (IAC)

[glider.]

IAC - Idle Air Control - An electric valve or stepper motor that's threaded, one turn of the valve is called a "step". It's controlled by output signals from the ECM to open and close as needed to allow enough air into the engine for starting and idle operation. It's function is to bypass the throttle blade in the intake and allow enough air to bypass the throttle blade to run the engine.(Throttle closed) The more steps, the greater the amount of air enters the engine through the IAC passages. It's that black unit you can see just inside and over the top of the air cleaner.
From time to time they get gummed up from the oil mist that enters from the engine breathers and need to be cleaned out. If you look inside the throttle body there's a hole in the upper portion and that is what needs to be cleaned out. You'll usually see some black gunk come out when you clean it. The problem it gives you when it needs cleaning is an erratic idle speed and stalling and usually does not set a code unless they fail.
A can of carb cleaner will do the trick here. One thing is to blow the carb cleaner out with some low pressure air or the other sensors in the intake will set codes from the carb cleaner.
If you don't have any low pressure air to blow it out, just let it air dry for a while before turning on the ignition.

More on the IAC...

Harley Davidson Community

 

[rjsogard]

hello Mr. Data how do you test the IDLE AIR CONTROL I dont have the elect manual for a 06 wg i have this problem after and before alt stator/rotor failure. I did the cleaning procedures in self help. it was dirty. On the first start of the day it will start then after a min 30 rough idle and stall. Then threw out the day rough idle no stall. thanks rich

 

[glider.]

The digital tech is needed to test the IAC properly. Have you checked for an intake leak?

 

[rjsogard]

The digital tech is needed to test the IAC properly. Have you checked for an intake leak?

yes i did with starting fluid or is that too harsh? i will recheck it tonite i have a new batt thanks to the alt stator thing. I drained and added fresh gas from a different source. i will do the crank sensor ck and look for debris. Mr. Data this rough ilde happened at the same time the alt stator/rotor failed could this be tied together? also the new batt at idle is only reading at 12.96 it does advance above idle i guess a new batt doesent need to charge at a higher voltage 13,14 volt. thanks again.

 

[Hoople]

Alternator output (voltage) is a function of RPM. At idle you are fine having 12.96 volts. As long as it pops up when you twist the throttle, your good to go.
Sorry I can not tell you too much about the low idle.

Hoop!

 

[rjsogard]

Alternator output (voltage) is a function of RPM. At idle you are fine having 12.96 volts. As long as it pops up when you twist the throttle, your good to go.
Sorry I can not tell you too much about the low idle.

Hoop!

thanks jim my old batt was still good hd made me buy but i didnt have a load test on it but it started like the new bat well i will leave that alone for now. rich

 

[glider.]

yes i did with starting fluid or is that too harsh? i will recheck it tonite i have a new batt thanks to the alt stator thing. I drained and added fresh gas from a different source. i will do the crank sensor ck and look for debris. Mr. Data this rough ilde happened at the same time the alt stator/rotor failed could this be tied together? also the new batt at idle is only reading at 12.96 it does advance above idle i guess a new batt doesent need to charge at a higher voltage 13,14 volt. thanks again.

Starting fluid (either) isn't the best thing to use to do this. Carb cleaner would be better.

I can't see any ties to the alternator causing this idle problem.

The alternator puts out little at idle. As long as you see 12+ volts there and it rises up when you raise the RPM's to 13.5+ you're OK.

 

[rjsogard]

Starting fluid (either) isn't the best thing to use to do this. Carb cleaner would be better.

I can't see any ties to the alternator causing this idle problem.

The alternator puts out little at idle. As long as you see 12+ volts there and it rises up when you raise the RPM's to 13.5+ you're OK.

Hi Mr. Data i will use carb cleaner around the seals. other than raise in rpm what else shoule i take notice white smoke in exhaust? Do you think a spike in voltage zapped my IAC when the alt system went out? or do you think the seals expand as the motor heats up. I am trying to stay away from the dealer but i still have the ESP do you think this is covered PS i did change the plugs. and wires in march.

 

[glider.]

Hard to say if the IAC is totally at fault from here. It could just be in need of a proper cleaning and it's hanging up. Did you check for intake leaks thoroughly?

 

[rjsogard]

Hard to say if the IAC is totally at fault from here. It could just be in need of a proper cleaning and it's hanging up. Did you check for intake leaks thoroughly?

hi Mr. Data

I thought i did with the wrong stuff i just used what i had starting spray i just went out and got some carb cleaner and will try it again real slow around the seals thanks rich.