I have a question regarding the the interchangeability if the IACs. I have a 1994 F-250 with a 5.8l that I primarily use to plow our church parking lot. At the end of last season it started idling very fast. Not good when you are constantly shifting back and forth between drive and neutral.

I figured a bad IAC or vacuum leak. A retired mechanic at church looked at it and verified a bad IAC. He went ahead and replaced it with an Autozone TV205. The next time I went to drive it the high idle was gone but it seemed to idle a little too slow and died if I sat with it in gear, and my foot on the brake, for more than 30 seconds. It also starts harder and dies now that it has gotten cold.

So here is why I am curious about the differences in IACs. I looked up the TV205 and it is listed as being for 4.9l and 7.5l. The 5.8l is supposed to have the TV203 IAC. Could the wrong IAC cause the problem? Or is the differences in the IACs mostly connection configuration? Also, one of the other posts on this site mentioned that only a genuine Ford IAC should be used and that aftermarket units may not work. Is this true?

Thanks for any input.

 

Only difference in those two are that they are clocked differently for application, connector rotated approximately 90deg for mounting location.

Followed both fitment wise, yes one fits 4.9L/7.5L the other 5.8L both 94 model year used as vehicle, all three motors would be electrically the same in that regard 92 tru 96.

Either you have other issues causing the problem or the one you bought is not working as it should (I kinda doubt it but anythings possible), but you'd need to test to make the determination one way or the other.

You could simply exchange it first see if you gain anything doing so, odds get two of those in a row that are faulty be even lower than getting a bad one right of the bat I'd think.

 

Check and make sure its not clogged with some carbon as well, Sometimes even after you replace them some carbon that wasn't cleaned out can cause the IAC to act up as well.

 

Correct idle speed depends upon several things..

No vacuum or gasket leaks.
IAC valve and solenoid are functioning properly and the ports in the TB are not clogged.
TPS sensor is within spec.
Throttle valve(butterfly) stop screw has not been altered from the factory setting.

 

Those are some very good points as well that really should be considered, Its best to check all of those things before you go throwing a whole lot of parts at it, I just tend to forget about the important stuff like that allot of days.