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1987 - 1996 F150 & Larger F-Series Trucks 1987 - 1996 Ford F-150, F-250, F-350 and larger pickups - including the 1997 heavy-duty F250/F350+ trucks

IAC Question

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Old Oct 8, 2012 | 10:42 AM
  #1  
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IAC Question

The solenoid that controls the IAC, I'm assuming that plunger in there should be able to freely move in there or am I wrong? The valve itself seems to be working as with the truck running if I push on the valve plunger I can hear it suck more air and the idle increase. When I put the solenoid back the idle seems to increase leading mot believe that the solenoid isnt backing off and is stuck in position. I'm trying to figure out why my idle is still high. Even with the solenoid off though, which would mean the valve is closed all the way the idle still seems kinds high, about 850-900.
 
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Old Oct 8, 2012 | 12:25 PM
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Fuel Injection Technical Library » Idle Air Bypass (IAB) Have a read here.
 
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Old Oct 8, 2012 | 05:58 PM
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I've been playing with idle air motors for a couple days now and I can tell you that on the 3 I have, when you put the solenoid on the valve section it does open the plunger a bit.
2 are oem ford and one is a new aftermarket. I ended up putting the solenoid from the aftermarket one on a factory valve in order to get one that works correctly and is consistent.

Yes, 850 to 900 is high with the solenoid off, its high even if you had the solenoid on but not plugged in.

A little on the high side even if you had a functioning air bypass most likely, depending on what year/eng/trans you have and whether or not the ac is on.

You may have a vacuum leak, or incorrectly adjusted idle stop. If you search this forum for "high idle" you will find plenty of information on the subject.
 
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Old Oct 8, 2012 | 06:10 PM
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I thought maybe it was the idle stop screw because the TPS voltage at idle is slightly high but it seems to work good (voltage increases smooth when i manually open the throttle, and resistances seem good too. It just seems like the reason the TPS voltage is high at idle is because the screw isn't letting it close all the way. I just didn't want to back the screw out and fix solve the problem but not actually fix the real cause. Not sure if there is any way to actually tell if the screw has been previously adjusted or what. Only thing I can think o is the previous owner adjusted to fix a low idle issue. I dunno.
 
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Old Oct 9, 2012 | 07:14 AM
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What is the closed throttle TPS voltage?
 
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Old Oct 9, 2012 | 07:27 AM
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Slightly high at idle; 1.2v. Resistance at closed is slightly low too, 2.89k, but pretty much spot on at full open, between 340-350.
 
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Old Oct 9, 2012 | 07:41 AM
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In your other thread, listing the codes the OP has in KOEO and CM, you stated you have a Code 23, TPS voltage too high or low at closed throttle. I also asked what the closed throttle TPS output was. Now that we know it is out of spec. I suspect someone has moved the throttle stop screw.
 
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