I'm working on a 2002 Windstar 3.8l, it starts, runs and idles. I let it run at idle until it reached operating temp (fans kicked on/off a few times). I noticed if I softly tap the gas and remove my foot from the pedal the RPMs would start to run away (2000 - 2500) and stay at this high idle for 15 to 20 seconds before going back to normal. During this time I can hear it sucking in air. If I unplugged the IAC the symptom would go away. The IAC has been replaced, any ideas or direction as to what's going on and how to troubleshoot it. Also I have not checked any of the relays or fuses yet.

Here is a list of codes I pulled out of the PCM:
C1234, C1185, C1198, C1194, C1254, C1246, C1250, C1242, C1214, C1210, C1169, U1260, C1446, U1009, U1262, B1317, B1318

Many of them relate to the ABS Module. I don't think there is any connection to initial problem listed above. I have not checked the fuse or relay yet but am leaning toward the ABS Module needs to be replaced.

 

Hi rj,

Before replacing anymore parts might I suggest that you do some serious checking of your vehicle's electrical system.
Just because the vehicle starts and runs is no real indication everything with the electrical system is working correctly.

Your vehicle's idle problem and multiple ABS codes seem to indicate insufficient power available to the various components.
You could use a voltmeter to verify sufficient power is available to the vehicle's system or you could just start with cleaning all the ground connections you can see and find.

I wouldn't replace anything until it was verified defective. Low voltage to all the components involved is what appeared to cause all those codes to come up.

A reminder, a circuit cannot function correctly if only half of the circuit is capable of supplying a path. Which can mean the fuses might all be good, but full power cannot get to the components due to poor connections. AND the other half of the circuit is the ground side. So,,,,,,,,,,,what is common to all those codes? They seem to be lacking a good ground path.
If upon checking the output of the power relay no reason is found for poor power supply to the components involved, the only remaining thing to confirm is good grounds.

 

That was my plan of attack too. I have a volt meter and a test light. As I mentioned before I have not checked the relays & fuses yet but that will be the first thing to do. Then I'll start verifying good grounds and proper voltage at the electrical connections. I'm leaning toward it being a wiring problem because the owner has had it to many shops and the shops have thrown many parts at it already.

 

You seem to have a good handle on what to do and check Voltage drop testing should find it.
. If you would , we all would like to know what you found, thanks

 

So what happened with the new IAC, didn't it fix the problem?
If not were you able to isolate the vacuum leak you noticed?

 

Replacing the IAC did not fix the problem, currently I don't think the sucking in air sound is a vacuum leak, I think it's extra air being sucked in through the air box because the IAC is fully open but that's just my guess at this time. Next Sunday is when I'll have some time to work in it again.

 

Today I poked around on the 2002 Windstar 3.8L. With the electrical connector on the Idle Air Control (IAC) disconnected and the engine running, it would not immediately respond when giving it gas at the throttle body. It had no power and hesitated like it was out of timing. Unfortunately I didn’t see if the Intake Manifold Runner Control (IMRC) was working when I gave it gas. I did check that the plastic bushings are in good condition and the rods are in place on the IMRC. One thing I noticed was the front valve was not touching the set screw compared to the back one that was. I was not able to move the front valve with the rod installed but was able to freely move the valve with it removed. Again the valve would not touch the set screw. Is the valve opened or closed when it touches the set screw? How much movement should the IMRC (valves) have when giving it gas? I don’t see the IMRC wiring in the Haynes 36097 Repair Manual, may be I missed it. If someone has a wiring diagram of the IMRC it would be of great help.

Other things I checked was the voltage at the IAC. I was able to measure 12V on both pins with the key on, engine off. I was able to measure 5V reference voltage on the throttle position sensor and see the voltage slowly increase on the signal wire when I slowly rotated the throttle body valve. I applied a small vacuum on the EGR valve to see if it would stall the engine (open the valve), which it did. I connected a test light to the positive battery terminal/cable and with the other end touched engine block (it lit up), alternator (it lit up), IAC (did not light up), throttle body (did not light up).

 

How 'bout that purge valve in the return fuel line.... that's the one that's connected off your charcoal canister..... they're fickle and can get stuck open or closed.... maybe I'm stabbing in the dark here but fuel issues can be attributed to faulty emissions equipment

 

After months of snapping front and rear engine mounts and smacking the upper plenum up into the underside of the hood…I changed fuse 20 in the engine compartment fuse box. Voilahhhhhh, no more runaway idle. The amp looked perfectly fine, but for giggles and a lack of what else to try, I replaced it. Runs predictably again.

 

Good work, thank you for the update.