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Unplug Idle air control valve and engine dies (2.9L V6), Normal or bad valve?


wildbill23c

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I have an erratic idle, starting to lean towards a bad idle air control valve, if I unplug the valve while engine is running it immediately dies, I'd think it should still idle with the valve disconnected correct?
 


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sgtsandman

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Is the engine warm or cold when you do this? If I remember how the valve works, it makes a difference.
 

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Rpm's will drop and the engine can die.
 

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This might help some:

 

wildbill23c

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This is with the engine cold. During regular startup when its cold it should idle slightly higher and it doesn't do that either, it drops right down to a very low idle to the point where if I let it sit there for a few minutes it'll die. Out on the highway it will start losing power and get really sluggish. This morning I tried driving it and all it would do is just buck no matter what I tried to do with throttle input it would spit, sputter, and buck. Which leads me to that valve being bad. If I take it off the intake and knock it around or take it apart then put it back together it'll run and idle fine for a while until you give it gas then it usually goes right back to not wanting to idle high enough, and cuts out, bucks, spits and sputters on the road.
 

wildbill23c

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Unplugging the IAC right after start up with the engine cold, it immediately will die. Doesn't matter warm or cold it dies. But I thought it wouldn't matter after it was warmed up that sensors took over after initial warm up sequence so the IAC didn't do anything after that?
 

wildbill23c

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I get 9.5ohms at the solenoid on the back of the valve...which according to the standards is well within specs of the 7-13ohms. I took the valve off and tried to clean it thinking maybe that was the issue but it didn't seem to have any effect. The Haynes manual really doesn't give anything of use for this problem to really be able to troubleshoot anything and given the way the valve acted when I took the IAC apart (took the screws out of the solenoid side of the valve) pulled the 2 pieces apart and as soon as I did you could hear like a spring and rod release in it which leads me to believe the dang thing is sticking really bad so once its warmed up the valve isn't functioning properly leading to the idle issues and the power problems at highway speeds...I did order the valve anyways so we shall see in about a week what happens LOL.
 

RonD

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IAC valve is used all the time, computer has target RPMs based on engine temp, ECT sensor temp reading

After engine is fully warmed up it may idle at about 500rpms with IAC Valve unplugged, but should idle at around 650 with IAC Valve plugged in, 750 with automatic

While IAC valve is off the engine turn on the key and plug it in
Should be open all the way for start up
Unplug it and valve should close all the way, only moves 3/8" but should move
Unplug it and plug it in as much as needed to make sure its moving

You can test the wires now as well, should see 11-12 volts with key on engine off unplugged from IAC Valve
If not computer is not grounding it like it should

IAC valve gets 12volts on red wire with key on, the other wire is the ground from the computer, its used to reduce voltage to open and close valve, super acutate control, +/- 4 rpm
 
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sgtsandman

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Yeah, it sounds like it's bad. I've had to clean mine on another vehicle make but not because it was sticking. It had a screen on the up stream side that would cake up with crap over time and malfunction because of it. I suppose you could play with the old one a bit in order to see if you can get it working but either way, it sounds like it's time for a new one.
 

wildbill23c

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IAC valve is used all the time, computer has target RPMs based on engine temp, ECT sensor temp reading

After engine is fully warmed up it may idle at about 500rpms with IAC Valve unplugged, but should idle at around 650 with IAC Valve plugged in, 750 with automatic

While IAC valve is off turn on the key and plug it in
Should be open all the way for start up
Unplug it and valve should close all the way, only moves 3/8" but should move
Unplug it and plug it in as much as needed to make sure its moving

You can test the wires now as well, should see 11-12 volts with key on engine off unplugged from IAC Valve
Ron,

I'm getting about 11.6 volts at the wires on the back of the valve. Plugging and unplugging the valve without it attached to the intake isn't giving any movement at all which is why I assume that its bad since its getting power, and I was guessing that it should move or do something when I first turn the ignition on but the valve isn't moving at all when I plug the connector back in. I also cleaned the ports in the side of the intake as well...no change.

That valve shouldn't have any impact at highway speed or does it if it suddenly decides to work?

The solenoid itself seems to test out ok with the 9.5-9.7ohms reading as its within spec, so that valve itself just seems to be shot?
 

RonD

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Just as a heads up, there have been quite a few issues with 3rd party IAC Valve, better to get Motorcraft even at a wrecking yard, the same model IAC Valves were used on many engines
 

wildbill23c

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Yeah, it sounds like it's bad. I've had to clean mine on another vehicle make but not because it was sticking. It had a screen on the up stream side that would cake up with crap over time and malfunction because of it. I suppose you could play with the old one a bit in order to see if you can get it working but either way, it sounds like it's time for a new one.
Kind of what I think. I sprayed a bunch of carburetor cleaner in it and let it set for a bit and the cleaner came out clean, so there's something else going on, stuck solenoid, valve just plain stuck, etc. I got one on order but thought I'd play around with this one and see what happened, but nothing seems to get it unstuck.

Thank you for your assistance.
 

wildbill23c

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19K, 19D, 92Y, 91F
Just as a heads up, there have been quite a few issues with 3rd party IAC Valve, better to get Motorcraft even at a wrecking yard, the same model IAC Valves were used on many engines
Ordered an OEM, I had read about those IAC issues as well, and thought I'd skip the potential issues and get the right one LOL. Thank you for the heads up Ron.
 

RonD

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Ron,

I'm getting about 11.6 volts at the wires on the back of the valve. Plugging and unplugging the valve without it attached to the intake isn't giving any movement at all which is why I assume that its bad since its getting power, and I was guessing that it should move or do something when I first turn the ignition on but the valve isn't moving at all when I plug the connector back in. I also cleaned the ports in the side of the intake as well...no change.

That valve shouldn't have any impact at highway speed or does it if it suddenly decides to work?

The solenoid itself seems to test out ok with the 9.5-9.7ohms reading as its within spec, so that valve itself just seems to be shot?

Test each connector on the IAC valve to the metal case, should be no connection of course, if it has an internal short it could go wide open when driving

Voltage is OK on the wires

Yes reads like IAC valve is kaput
 

wildbill23c

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Ford Bronco II
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4WD
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Total Drop
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Tire Size
235/75-R15
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19K, 19D, 92Y, 91F
I tested to each terminal and ohms in spec, then tested to a ground and got nothing, so I assumed that part was good. I pulled the IAC off that was on the truck and I had read somewhere that there should be a D on the black plastic connector of the IAC, mine has a 7 on it, but does say Ford and is an original Ford IAC, but wonder if someone swapped it with the wrong IAC off something else, if that's even possible.

I had thought about pulling the IAC off my Bronco 2 and putting on the Ranger just to see but not sure if that would be a good idea, then I'd have to find a new gasket for the Bronco 2 and I daily drive it so I don't want to go screwing it all up LOL.

I am under the same assumption that IAC is a paperweight. I get absolutely no movement when plugged in with the key on, even bench testing with a 12V power source I got nothing....anyone need a paperweight IAC LOL.
 


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