cliffyk

It won't throw a code immediately, it can take up to even as much as 30 minutes runtime.

Have you run the tests I listed above?

dazednconfusedj

Yes i did, and everything checked out OK.

I'm kinda wondering if the pigtail going to the IAC has come a little loose from me unplugging it so many times when i was messing with the car.

The wires going to it look a little bent up, but it reads >12v with the key on.

I have had wierd things happen with electronics with loose or bad connections before.

I've seen it before with stranded wire where it will show 12v, but as soon as it pulls any type of current it ****s out.

cliffyk

This is a possibility.

If you can back-probe the connector, or pierce the insulation¹, you can measure the AC and DC voltage with the plug connected to the IAC and the engine idling--this will then be applying the load of the IAC to the line.

These measurements should be around 5.0 to 7.5V in AC mode, and 3.5 to 5.5V in DC mode, maybe more, depending greatly on the response and input impedance of your meter.

The IAC input resistance of 6 to 13Ω means that the DC load is 1.0 to 2.0A, this is pretty high and a wire down to 1 or 2 strands might not pass enough current to operate the valve--this would result in the measurements described above be very low as compared to the listed ranges.

The only way to be 100% sure would be to "look" at the signal with an oscilloscope...

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¹ - A couple of stout sewing needles or pins can be pushed through the sires to "tap" the signal. If you want to get serious about this sort of thing buy a pair of these:



They are great for poking around in a car's electrical system. When you remove them (or the needles/pins) use a dab of dielectric grease to seal the puncture.

dazednconfusedj

I want to thank you cliffyk for your help, it has been extremely helpful and beneficial in learning a thing or two lol.

So the resistance on the IAC body measures normal at 11.2 ohms.

When i backprobed the connector going to the idle air control while the car is running and idling, Im only getting 2.5 AC volts... What could that mean?

dazednconfusedj

Nevermind, I'm getting 6volts in AC and about 2.5 Volts in DC, sorry. I have no idea what all this means

cliffyk

The good news is it means the PCM is delivering a signal to the IAC--which points back to an air leak or partially open throttle valve. Make sure the throttle is closing completely (not actually completely, but coming up against the stop screw), and do a double check for air leaks after the MAF. The PCV valve can sometime be stuck open and create problems.

You may want to remove the IAC and make certain there are no restrictions and that if the gasket is one that only has one port hole (most have two, however I have seen some with just a single hole) it is installed correctly.

If none of the above work you'll have to get it to a shop with a diagnostic scope, or Ford's IDS tools.

dazednconfusedj

Did a smoke test on the intake at work, nothing was leaking...IAC is good, MAF is good and clean...

Also did a fuel pressure test the other day and drove around with the gauge on my windshield, Fuel pressure was good...

Everything seems to be mechanically correct on my part, I've sent my tunes and stock tune back to SCT, and im awaiting an email back from them....


Any thoughts?

AVandergrift

there was a thread on this same thing happening with a 98 Cobra. Mine started to do the same thing which is what caused me to start looking into it.

When I'm coming off the freeway - if I just dump the clutch the RPMs drop all the way down - occasionally even just dropping to zero. if not zero - then the RPMs drop to 400 or so, then up to 900. Here is a you tube link from another guy on the forum of it happening to his.

http://www.youtube.com/watch?v=13S0_QlgYwY

Thoughts?