iac only works upside down?? - MustangForums.com



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Old 03-20-2017, 07:00 AM   #1
schecterplayer
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Default iac only works upside down??

OK everyone I've got an issue AGAIN with idle on my trick flow stage one car. The car has been idling perfect after I fixed the idle reset issue. I had the car sitting after the snow we just had in MD. I go to start it up yesterday and the damn thing surges and dies! Idle is crap again. I started by checking for a vacuum leak to no avail. I checked tps voltage and it's. 95. I cleaned the iac and actually made it worse. (aftermarket iac from latemodel restoration). So I proceeded to reset base idle again and it never worked. I was pulling my hair out not knowing what was wrong. I read somewhere that somebody had flipped their iac upside down and solved all their idle issues. So I thought why not and did it. IT FIXED IT COMPLETELY. The car even starts faster, holds a great cold idle, runs smoother and just performs all around better. This is the first time I actually see the iac doing anything like what it's designed to do. If I unplug it, the rpms drop like they should. They never did that before. I'm so confused. Is It a bad iac?? Do I need that adjuster plate? I'm happy it's working now but it's not supposed to be upside down as far as i know
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Old 03-20-2017, 07:48 AM   #2
88 orangepeel notch
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That's a new one to me lol. Did the IAC have any buildup or dirt inside that would cause this ?
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Old 03-20-2017, 07:59 AM   #3
schecterplayer
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That's a new one to me lol. Did the IAC have any buildup or dirt inside that would cause this ?
lol it didn't have anything. It's only about a year old. The valve moved freely and felt normal.
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Old 03-20-2017, 08:28 AM   #4
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Your IAC is junk,


The actuator is going kaput. The reason it runs better upside down for the moment is because the manifold vacuum is pulling on the wrong side of the actuator spring. Dont be surprised if the idle starts getting away from you .
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Old 03-20-2017, 08:52 AM   #5
schecterplayer
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Your IAC is junk,


The actuator is going kaput. The reason it runs better upside down for the moment is because the manifold vacuum is pulling on the wrong side of the actuator spring. Dont be surprised if the idle starts getting away from you .
thanks for the info! I figured as much but I wanted to make sure. So in theory, if a new iac is working 100% I should have the same performance as this one is upside down? Like I said I never remember the rpm dropping when I unplugged it. It's never started this well when cold and never idled this smooth
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Old 03-20-2017, 01:00 PM   #6
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lol are you sure it wasnt on upside down to begin with
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Old 03-20-2017, 01:03 PM   #7
schecterplayer
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lol are you sure it wasnt on upside down to begin with
🤔 well it was put on the same way as the stocker lol so I think so
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Old 03-20-2017, 07:04 PM   #8
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Spend the money on a Motorcraft IAC. Those cars are notorious for bad IACs. I've tried a few BWD ones (all junk) that lasted a few months, tried a Duralast one which seemed ok, but finally spent the money on a Motorcraft one which is by far the best unit. It's the most expensive, but it's the best. Also, if the IAC is over working it will not last as long. Be sure your base idle is set correctly. The Duralast ones have a lifetime warranty, so you can try it out and see if it works. Worst case just take it back and buy an extra gasket.
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Old 03-21-2017, 03:48 PM   #9
schecterplayer
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allright fellas im about to throw the car off a cliff. i got a motorcraft oem iac. threw it on the car, started the it sputtered but caught itself. i reset the idle to 600 ish, unhooked the battery for 20 mins and it held it perfectly and performed perfectly. i parked it at a gas station and went to start it up and the surge is back and it only got worse the second time i started it. I hate this car so much right now lol
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Old 03-21-2017, 06:01 PM   #10
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Hey sorry, but I didn't see your original thread. What's the overall problem? Also, did you do a base idle reset with the car warm?
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