I have the 411 code: cannot control idle during low test

So according to my Haynes manual about 10.5V should be going to the IAC and there should be somewhere between 8 - 13 Ohms of resistance.

My IAC was reading 11.77V and 11 Ohms. Is the voltage far enough off to make a difference? It shouldn't right? As long as it's in the Ohm range I think. Does look pretty crummy inside but not terrible. What should I clean it with or what else could cause this code?

Thanks guys, it's a quick one.

 

There is a lot of information on this forum about testing your IAC, I will give you a quick summary.

Don't worry about the haynes manual's 10.5 volt supply, nobody ever seems to get that voltage.

You are in range with the ohms, but that does not mean it is working, or working correctly. If it was open or grounded then it would be bad for sure.

A quick test to see if its working is to unplug it with the truck warm and running at an idle, it should either die out or almost die. If your base idle isn't right or if you have a vacuum leak somewhere it might not drop that many rpm's. One way or the other it should make a very noticable difference when you unplug it.

There are different opinions regarding cleaning the IAC, sometimes it works, sometimes not. Its quick and cheap to give it a try. The passages in the throttle body may need cleaning as well. Throttle body cleaner would probably be best to clean it with, I just used brake cleaner since it was handy.

If you have to replace it, you are better off with one from a junkyard or from Ford. New aftermarket ones are usually worse than the old ones. I can vouch for this as the new Duralast one I bought was junk, both the valve and solenoid. Ended up rapping the solenoid on the old one with a screwdriver handle after cleaning didn't work and its been working fine.

I don't know it this is true for 302 engines, but for the 4.9s there is a diode in the wiring running to the Iac on the 87 and 88s, and maybe some '89's. Later Iacs have the diode built into the solenoid and are marked with "DD" in the plastic near the connector. I'm not positive on the change over year but their is a Ford TSB on the subject. You would want one with the diode in the solenoid if the same thing is true for 302's.

I haven't read anyone mentioning it yet, but you can also hear when the motor is running. On my 4.9 I can pop the air cleaner open at the box and the intake hoses amplify it making it easy to hear. Oddly, the old, possibly original, one is actually quieter than the new one I tried.

 

Some good info from another forum: IAC Cleaning - FSB Forums

 

Sorry Ive been out for quite a bit but thanks thats good info. The cleanin I did seemed to do it a justice. But I still wanna try what you said to do. Thanks again