Code 412???

[Husky44]

Car's been running a little rough, especially when cold, doesn't hold idle until engine warms up. At cold start, it tries to idle around 600 rpm; when warm it's closer to 800 rpm.

Ran codes, KOEO came out clean, KOER gave me the following:

412: Cannot control RPM during KOER high RPM check
314: Thermactor air system/fault during engine run self test/left side
311: Thermactor air system/fault during engine run self test

Smog system is pulled, so I assume 314 and 311 are just sensing that stuff isn't there? Sow what is 412, and what do I do to fix it?

 

[HISSIN50]

Is the IAC plugged in?

If so, has it been cleaned recently?

 

[Husky44]

Is the IAC plugged in?

If so, has it been cleaned recently?

OK, so I really know what IAC means, but others on here may not, and I want to make sure this post helps other people as well, so why don't you tell everybody what IAC means...

 

[HISSIN50]

For general knowledge, the IAC is the Idle Air Controller. Below is a picture and a write-up on cleaning it. Note that IMHO one should NOT clean the IAC unless prepared to replace it. Sometimes they crap out after being cleaned. However, if someone looks inside the thing and it looks like a chimney, there's not much choice.

Ford Mustang IAC IAB - Solving your idle problems

 

[Husky44]

For general knowledge, the IAC is the Idle Air Controller. Below is a picture and a write-up on cleaning it. Note that IMHO one should NOT clean the IAC unless prepared to replace it. Sometimes they crap out after being cleaned. However, if someone looks inside the thing and it looks like a chimney, there's not much choice.

Ford Mustang IAC IAB - Solving your idle problems

That's exactly right, just as I knew it to be...now I just need to go out to the garage and perform the step-by-step procedures in the link you cited to verify that it goes through the procedure in good detail, and doesn't miss any important steps, to help out others...

Thanks, HISSIN50!

 

[HISSIN50]

It's nice when we can help the newer guys out.

IIRC, that write-up doesn't mention a lack-of-idling-when-cold as an IAC issue, but it is. You're older like me - the IAC performs part of the function of a choke.
It also increases the idle for the AC and it performs a dashpot function (another carb term lost on the kids).

FWIW, I like to use WD40 instead of carb cleaner. I fill the thing up with WD and let it marinate for about 15 mins. Then rinse and repeat. It takes several times to get it clean. Then on the last round, I use a quality cotton swab (you don't want cotton lint stuck inside there) to 'swab' out the guts. You'll get a lot more crap out of it. Then I rinse it once more (no soaking) with electrical contact cleaner and put it back in.

 

[Husky44]

Thanks for the tips! Now I just need to find time to do it. Waiting for my last meeting that was supposed to start at 9:30 pm...busy the rest of the week, then flying out Friday to go to NY for my Grandma's 90th birthday party...I may have to do it after it's parked for the winter.

I'll post some results when I finally get it done.