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A few weeks back my 2002 F225 stalled while idling at anchor. When restarted it was running on four cylinders. Upon inspection, the top coil was cracked and melted. Replaced it and it ran good for a short time and melted the top coil again. YDS was showing a bad Intake air pressure sensor. Replaced that and it was still throwing the code and heating the top coil. Read a post by Rodbolt about a sticking IAC issue that will over current the ECU, ruining it which in turn would ruin coils as well as the IAC. Ran the diagnostics on the IAC Valve and it failed. The ECU was also sending a constant ground to the top coil. I installed a brand new ECU and IAC Valve today and now the motor is idling great without heating the top coil. The problem is that the IAC Valve gets hot while it’s idling. I can keep my hand on it, but, it’s not warm… it’s hot. Does anyone know what the normal temp for the IAC Valve is and what might cause a brand new one to heat up? I’m concerned about toasting another ECU, IAC, and Coil. I want to make sure it’s right before I go for a test run. Thanks for any thoughts, John I
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they get fairly warm normally.
typically I will use them if they remain under the 200* reading on my temp gun.
I have seen the ISC melt all 6 coils and the holder just before smoking the ECU. -
Thanks Rodbolt17. I'll check the temp and run both yds tests on the IAC valve just to be on the safe side. The coils are staying cool now and the motor seems to be running well. I guess close to 200 would feel pretty hot. I'm hopeful that there's nothing up the line still wrong that resulted in these problems. i.e. short in the harness. Thanks again!Comment
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as your not posting about idle issues don't worry about shorts.
at key on both sides of the stepper motor are hot, the ground path is made internal in the ECU.
if one ground path were to short to ground the stepper would run in that direction all the time.
remember the ECU simply sends a request, it does not monitor the physical position of the valve.
if the desired idle doesn't occur it keeps requesting(grounding).
the first sign that the ISC is failing is when you don't hear the ISC "rattle" at engine shut down.Comment
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Great, I'll run the tests and if all's well, I'll take it for a ride today. Thx!Comment
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Spent most of the day on the water. I had this motor since 2006 and today it ran better than it ever did. They must have made improvements to the ecu because I picked up 400 rpm and 4mph on the top end. Thanks again Rodbolt17 for your help. Your post in another thread gave me the clue I needed to make this repair. AAA+++Comment
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