IAC unplugged?

[86ltrain]

I have done searches but couldn't find a direct answer to my question, if i unplug the IAC plug with the engine running, what should happen? The reason I ask is my 93 4.0 idles roughly and at about 550-650 RPM's. I think this is too low but I cannot adjust it...or I know I shouldn't. I warmed up my engine today to operating temp, unplugged the 2 wire connector and nothing changed, I plugged it back in, no change. Anyone else done this with an IAC they know is good? I have checked it according to the manual and it checks out ok, I have cleaned it also but can still see some carbon inside the body and on the plunger. Thanks for any feedback.

 

[Donnie strickland]

If your IAC is working correctly, your idle should drop (perhaps to the point of stalling) when you unplug the electrical connector.

 

[darkchicken]

I can only offer 5.0L experience, but I'm pretty sure it's the same setup on the 4.0L. Clean, clean, clean. That and make sure everything else is tuned up. You probably won't hear a drop in RPM by unplugging the IAC. For the 5.0's, there is an aftermarket plate that allows you to adjust the RPM, I'll look to see if it fits 4.0L too. You may also be able to tweak it with timing and/or TPS.

 

[Broaner]

I have a similar situation except with a high idle. Mine likes to settle at 1700 sometimes dropping to normal but its getting more rare every day. When I unplug the IACV nothing changes except cold start changes. Ideas?

 

[trhull]

Found this on rangerpowersports.com I'm a member but dont post anything there; I really dont like the way their forum and tech stuff is set up. But this may be able to help you, maybe not, I haven't tried it. http://www.rangerpowersports.com/tech/?p=44. TRS all the way we got a good thing going here.

 

[bottledgt]

i have always noticed a decrease in idle when unpulgging it. there should be 'some' change

 

[Wicked_Sludge]

your idle should drop when you unplug your IAC solenoid. 86ltrain, it sounds like your IAC is stuck in the closed position. if you have an analog voltmeter or a 5v test light you can confirm if the IAC is receiving a signal from the computer...but chances are good the IAC is bad.

 

[Broaner]

Thanks for the input guys. Couple Q's.

What value should the IAC be recieving at idle? Does it fluctuate?

Somewhat related, whats a good price for my motor, trans, T-case set with 120K on it. I'm getting close to getting into a 302 buildup.

 

[86ltrain]

I have checked the input voltage and it looked fine. I tested the IAC with an Ohmeter and it checked out ok, but I don't think that is 100% foolproof. I have checked many times by unplugging it and every time there is no change. My truck does high idle as it should when cold though, doesn't the IAC control that? Thanks...