Sulli8888

[QUOTE=fltdriver;4224898]IAC controls air flow at idle (pretty much a new version of a choke). Computer controls the IAC causing higher idle until the ECT (Engine Coolant Temperature) sensor reads a standard operating temp of the coolant inside the engine.

To test the IAC:
First unplug the connector then start the truck (when completely cold), if your initial idle is different then your IAC is not functioning properly. To verify IAC solenoid is bad: Use an ohm meter to check the solenoid by attaching the positive lead to the VPWR (vehicle power pin) and the negative lead to the IAC pin.

• Your resistance reading should be between 7.0 ohms and 13.0 ohms. If your reading is off, your IAC solenoid is bad.

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Ok I started the truck cold with the IAC unpluged. it idled at 550-- 600. I turned off motor and pluged the IAC back up and no change. I would think cold it should rise up to 1000 or so as my other Fords do???

fltdriver

That test basically just rules out the IAC as the problem. As I asked before was it doing this (no rev at initial startup) before you replaced the ECT sensor?

If this is the only issue your having and it doesn't affect anything else I would say not to worry about it if you can (if you're like me you'll keep digging until you break it or fix it) but to pay close attention for any other abnormalities that may surface.

Sulli8888

yes it was like this before the new ect. And yes i know it's something simple. I want it to idle up at cold like it should just not sure which sensor controls that. This winter it may need it or it would die out?

Sulli8888

Ok, I started it idled about 550--600. Turned it off. Unplugged the IAC plug, started it and the idle was the same??? So does that mean I move on to a different sensor?

fltdriver

Correct, if it runs the same at initial idle without IAC as it does with then it's functioning properly. Didn't re-read all of what you've done but the next step I would take would be testing the TPS voltage, .9-.97v closed throttle, 5v WOT, smooth increase as the throttle is opened up.

Sulli8888

I dont know how to test voltage stuff. Im still learning from this site.
A girl has her limits ( lol ) but I am trying my best. I was just hoping it was a sensor that idles the truck up at cold until it warms some?????

fltdriver

There is a post by Chris 1 on how to properly test the TPS that is only a few down from this one, pretty simple. Take a multi-meter and ground the black lead and poke the red one into the wire, then open the throttle up and watch your voltage.

Chris_1

iTrader: (1)

It's vaguely possible that you did have a problem with your ect sensor - and still do. Sometimes brand new parts are faulty. Or the wiring to it may be bad.
Also do like fltdriver said and test the TPS just in case.
It's the computer that'll idle it up, but it depends on the sensors to tell it what's going on. Getting yourself a little $15 -20 multimeter and learning to test things will save you a lot of money on parts and also give you a much better understanding of how everything works.
I didn't read the whole thread (sorry, that durndle or whatever it is you're wearing kept distracting me lol) but I just wanted to check - you changed the temp sensor, not the sender - right ?
The sensor is just above the thermostat housing on the pipe, the sender is in the intake more towards the driver's side of the motor.

Sulli8888

Yes, I did the change on the temp sensor just above/ behind the
thermostat housing. I changed it because it started flooding at startup and the fixed it. I have cleaned th IAC but was told I may just need to replace it? Runs great nothing wrong except idle idle not raising at cold startup. And thanks for the comment about being distracted LOL.

Chris_1

iTrader: (1)

You're welcome.
I'm not much of one for throwing new parts at a truck to see if it works, but a fresh IAC wouldn't be a bad thing and mat work. It would be nice if you had a known working one to try on the truck to see what happens before you buy new. Wonder if the one from the Bronco would match up ? They're both 5.0 and pretty close in years. If the Bronco idles up properly I'd be tempted to swap IAC's just to see if it makes a difference before I lay out cash for a new one.