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Discussion Starter #1
I'm posting this for my brother (3855). It seems that when he is cruising along in his Bullitt at speed (2K rpms) and puts in the clutch the rpms don't come back down...ever. In order to get them back down he has to put the car back into gear and brake until the rpms are back to 1K. He says it does it pretty much every time. Inside the engine compartment he says that he can see the throttle return, but even then the rpms don't drop. So, what's wrong with it? IAC is the only thing that I can think of, but does it flow enough air to maintain 2-3K rpms?
 

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Clutch not adjusted correctly and dragging?

And how does he "See inside the engine compartment" running along a 2000 rpm?
 

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Throttle Sticking

My 5.0L had a throttle positioning sensor replaced and had the computer program reflashed to correct "a bad bit in the program", so I was told, for a problem like you described. Except mine was random, and would correct if the car was shut off and restarted.

One guess is that the "butterfly" in the air intake is sticking, even though the throttle cable returns.
Check it with the engine shut off.
Undo the hose clamp and remove the plastic snorkle from the engine.
Move the part that the throttle cable pulls on and look at the butterfly valve open and close. The operation should feel smooth and not bind or seize while opening or returning to a closed position.

Let us know what it turns out to be.
 

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I had this problem with 1152 on the way to and from the SF Nationals. When I got back I took it in for the Ford guys to work on it. They started with the IAC, then some other intake motor modulator device (I have forgotten the name), and eventually replaced the computer. The last item solved the puzzle. :confused: It could have been anyone of the items, and the tech advised me it could have been some others as well. They throw similar/same codes... DUH! I have a shop in Arlington that used to do all of 5 Star Ford's Used car maintenance if you/he wants a referal. So Fords and Mustangs, and their peculiarities are nothing new to them.
 

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Has he cleaned the butterfly on the throttle body lately?? I did on mine, and once the gunk was all gone there was just the slightest bit of air getting in and it caused this problem for me. All I had to do was adjust the screw on theside of the TB and the idle came back down to normal(yes, even when I shifted). Hope this helps.
Kerry
 

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Discussion Starter #8
I told him to pull the rubber snorkel off the TB and to check that the plate is still moving. I doubt that it is the problem though or else the car would re-accelerate once you let off the brake and it doesn't. I'll also tell him to reset the computer and clean the IAC. If it is still not working then I'll have him replace the TPS.

Would an IAC stuck wide open allow enough air for the engine to maintain 3K rpms without a load (clutch pressed in)? Maybe since the engine is already turning at that rpm it can suck enough air through it.
 

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5111 said:
I told him to pull the rubber snorkel off the TB and to check that the plate is still moving. I doubt that it is the problem though or else the car would re-accelerate once you let off the brake and it doesn't. I'll also tell him to reset the computer and clean the IAC. If it is still not working then I'll have him replace the TPS.

Would an IAC stuck wide open allow enough air for the engine to maintain 3K rpms without a load (clutch pressed in)? Maybe since the engine is already turning at that rpm it can suck enough air through it.
Dee, what I am saying is....if he cleaned the throttle body, the butterfly is not closing all the way and needs to be adjusted with the screw next to it. The TB is used to having the gunk there between the butterfly and the TB. Now that the gunk is gone there is an ever so small opening that used to be gunk and now the extra air is getting in. I know it sounds weird but that is all it took to get my RPM's to drop back down when I let off the gas.

What the hell, it is just the turning of a screw and doesn't cost a dime. If it doesn't work, then try something else.
 

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Discussion Starter #11
Kujo362 said:
Dee, what I am saying is....if he cleaned the throttle body, the butterfly is not closing all the way and needs to be adjusted with the screw next to it. The TB is used to having the gunk there between the butterfly and the TB. Now that the gunk is gone there is an ever so small opening that used to be gunk and now the extra air is getting in. I know it sounds weird but that is all it took to get my RPM's to drop back down when I let off the gas.

What the hell, it is just the turning of a screw and doesn't cost a dime. If it doesn't work, then try something else.
I understand what your saying, but he has not yet cleaned it so I'm not sure if that will be it.
 

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Discussion Starter #12
BlackBullitt5583 said:
If the IAC was stuck open, the car would die when coming to a red light.
The car would not die if the IAC was stuck open, it would die if it was stuck closed, right. The IAC allows enough air through the bypass so that the car does not starve for air when the TB blade is shut. At least that is how I understood it to work.
 

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Throttle stuck OPEN? I guess I can't see what the problem is here!! Just learn how to power slide around corners and you're all set!!
 

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5111 said:
I'm posting this for my brother (3855). It seems that when he is cruising along in his Bullitt at speed (2K rpms) and puts in the clutch the rpms don't come back down...ever. In order to get them back down he has to put the car back into gear and brake until the rpms are back to 1K. He says it does it pretty much every time. Inside the engine compartment he says that he can see the throttle return, but even then the rpms don't drop. So, what's wrong with it? IAC is the only thing that I can think of, but does it flow enough air to maintain 2-3K rpms?

Mine did exactly the same thing in July, stayed at about 2000 rpm even with clutch not engaged. I had read about this (sticking IAC) after doing a search on this board and figured I would try to clean the IAC. So I cleaned it with seafoam first, then brake-clean and blew it out and it has been fine since then, rpm's drop to where they should between shifts and at stoplights. Cheap and easy to do before spending any money on diagnosis or parts...John R :cool:
 
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