IAC? Vacuum leak? Two problems or one?

lrsudog

Registered User
Having an idle issue with my SC. Occasionally, once warmed up, the idle will drop very low (It's an AOD) and start to idle/run very rough, almost like it is running too rich. If I stay idling long for more than a few minutes in this condition, the "Check engine" light will come on. If I shut down the engine and restart it, the idle returns to normal.

Also, when I stop and take it out of gear, the engine idle will climb to 1500 or so, then drop to almost stalling, then back up, and so forth, almost like there is a vacuum leak. It seems only to do this when warmed up, and when it is in gear, I do not notice it happening.

So, I've clean the gunk out of the Idle bypass valve, and checked for vacuum leaks. All the vac lines are tight & new, and it seems to only happen when warm.

What's next? New idle air bypass valve? I have the factory shop manuals, and a quick look through didn't tell me if the Idle air bypass valve is the same as the "IAC" that seems to be giving a lot of people fits. If not, where is the IAC located?
 
lrsudog said:
............................
I have the factory shop manuals, and a quick look through didn't tell me if the Idle air bypass valve is the same as the "IAC" that seems to be giving a lot of people fits. If not, where is the IAC located?
They're one and the same.
 
Iac

Intake Air Control (sometimes referred to at the Idle Air 'bypass' Control) is the IAC. It is located on the Throttle Body just before the Throttle Position Sensor. I believe the electrical test of the IAC is to ohm it out and it should read between 7-13 ohms. The inside can be mechanically broken or leaking due to carbon build up or cracked sealing material (plastic?) Cleaning can sometime fix the leaking piston. If it ohms other then the 7-13 ohms, replace it. Do a search of the forums for "poor idle" or something similar to get more info.
 
You guys rock. I had already cleaned it, but it seemed to have a rust colored build up on the diaphragm side. That can't be good.

Looks like I'll be going to Ford for a new one.


Thanks for the info.
 
Back
Top