Vehicle: 1997 Ford Explorer, Vin E, 4.0L SOHC with 91,000 miles.
Symptoms:
When vehicle is started on COLD start only;
Vehicle starts fine (within first couple roll-overs.), idle speed goes up to 2200 rpm and runs for a few seconds then it starts to idle down and almost dies just below 500 rpm then engine revs up again just before it dies. It goes up to around 2000 rpm stays for few seconds and then idles down again. It does this for about a minute to sometimes three minutes. Seems to depend on how cold the outside air temperature is. It finally stabilizes and idles around 1000 rpm. After the engine is warm it idles down to 650 rpm in park. It seems to start and run fine right away when the engine is still warm.
What I have tried:
I first replaced the fuel filter and air filter. Then I replaced all the O2 sensors (4). Then I read on this forum that the O rings in-between upper and lower intake could be bad or leaking. I replaced them. I cleaned and checked the EGR valve (seemed to be working correctly using vacuum pump to test). I replaced the PCV valve. I cleaned the throttle body, MAF, and IAC valve with throttle body cleaner. I checked the ohms of the outside air temperature sensor and it was right on with my Chilton manual. I also checked the ohms of the IAC it was in-between the specs in my manual also. The vehicle still has the problem. I am ordering a scan tool so that I can monitor the sensors but I thought someone else may have a suggestion.
Thanks Terry

 

Since your symptoms mimic those of leaking lower intake manifold o-rings, I would look for any possiblity of un-metered air leaks into your engine. You will need a scanner that is capable of monitoring your short term fuel trims to troubleshoot it. Hopefully the one you get has that capability. While monitoring your fuel trims, spray propane (I found the $10 torch bottle from Wal-Mart works pretty easily) around your engine. Obviously you don't light the torch Since it has a long tip with an adjusting wheel it give you the ability to direct the spray where you want it and turn it on and off instantly. What you want to watch for is sudden changes in your fuel trims between spraying the propane and not. Sudden changes indicate an air leak in the vicinity of where you are spraying the propane. Try it everywhere the possibility exists (on top of engine, around PCV hoses and anywhere else you can think of). That is the method I got from Ford's TSB when the leaking o-rings first became an issue, long before ONP 00M12 was issued. I used it to track down my leaking o-rings. It took about 10 minutes to confirm the leak.