Another sensor you could check is the intake air temperature sensor. Mine's on the driver's side of the lower intake manifold near the front of the truck. My truck does the same thing, usually when it's cold. This summmer, I drove it for a bit with the iac disconnected and the rpms would drop really fast when I shifted. The drawback to that is that the computer still think's it's connected and richens the fuel right when you start the truck, and so you have to give it a little gas to keep it from stalling out. That went away after it warmed up. My truck ('87 F150 5.0, 4sp man. od.) has a spacer between the IAC valve and the throttle body with two allen head screws in it. These seem to control how much air is let by the throttle plates, and thus control idle speed. You could try to close these off a little, if you have the spacer there. That spacer may have been an '87 only thing, but I haven't seen any other 5.0's so I don't know if others have it or not. I know my dad's 4.9 does not have one. Hope this is a help.

 

Mine once in a while does it also. If I let it sit for a few minutes and restart it goes away. What do you mean you can't clean your IAC? Are you talking about that bogus protective film that is also on the T-body to prevent carbon buildup? If you are going to replace it anyway, why not just clean it first? For a code scanner, all you need is a simple "mechanical" volt meter. Hook it up and watch the needle bounce back and forth. Tells you the exact same thing as a $25 scanner from wal-mart. Chances are, it wont help anyway with your idle problem.

 

There are two types of IAC valves used, a cleanable one, where you can clean it on the inside, and a non-cleanable one. Mine is the non-cleanable. I am not refering to that coating.


Primary rig is Green Thunder:
95' F-150 XLT 4x4, 302, 5 spd, MSD 6A, Flowmaster Exhaust, Sunroof, Clear corners w/ Diamond headlights, CD player with 2 10" subs and some 32" BFG Muds .

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Justin - One Happy FTE Member

 

Update:

I was reading my newest issue of Four Wheeler and came across the section where readers can write in questions about their trucks problems. Someone wrote in with the same issue. He has a 96 F-150 4x4 <a href="http://www.motorhaven.com/">302 </a>with a manual transmission. Just like mine except his is a 96. He describes the same symptoms that I have. He also stated that he accidentally found that if you remove the speedo/dome light fuse, the problem goes away. I tried that today, and sure enough the problem goes away when you pull that fuse. The magazine came back in response and said that the idle air control valve solenoid is sticking internally. It may or may not send a computer code. If you can electrically unplug the solenoid while the engine is running with the rpms stuck at high, that'll prove it's sticking. If the rpms drop, and it almost dies, that isn't the problem. The part I'm not sure about is that I don't know if my IAC has a solenoid. As i said before my manual shows the two IAC's, cleanable and non. They both have a picture with an internal view. The cleanable one has a solenoid being pointed out, and the other doesn't. On the closed one it just says it has a diaphragm and rubber damper. Should I just get a new IAC?

 

If it's electrically controlled, it is a solonoid. The solonoid should be independent of the valve itself; it should be screwed to the end, and pushes on a shaft going into the actual valve. Cleanable or not, it shouldn't matter, the solonoid is the electrical device that makes it work.

 

Sweet, I'll go pick one up.

 

72 dollars for a new one with a gasket! Ouch.

 

Went to fordpartsonline.com and found that they have the same part for 47.20 instead of the list price of 69.92. I went to my local dealership with the printout and after a little negotiation, he dropped my price down to 54 bucks. He said 47.20 was his cost supposedly, and he's really surprised that it's available to me at that price. Don't know if that is BS or not but, I got a 15 dollar credit on my card, works for me.