I had a similar problem even though I've had the O2 sensor and about everything else on my 2001 SE7 replaced recently. Switched to non-ethanol gas and the problem stopped immediately. Maybe a coincidence, since I've also had a rodent infestation. Perhaps the nest fell out of the throttle linkage as Mark G mentioned.

 

I guess I ve solved the problem. I ve changed the IACS , installed o2's and configured all sensor values with T4. As a result I got normal idle speed and injection. Thanks to everybody!

 

Where did you find a T4? You can't be in the US.

 

You are right. I am from Moscow, Russia. And here you can find some T4's

 

OK, the problem is back. And it appeard after off road riding in mud. The interesting thing is that last time it appeard after similar situation and was solved by a simple ecu reset with t4. The question is: why do I need to make reset so often? What is it caused by? The engine compartment was not flooded in deep water and the wiring and ecu seem to be dry

 

Did you get the alternator belt wet? Slipping maybe causing charging/voltage to dip?

 

The alternator belt is fine. The problem was caused by IACS conus which was smaller(not the original one) than the hole and fell into the air intake. I fixed it quickly and everything was fine. But not for a long time... After I took my truck from service, where I replaced the camshaft and oil pump the idle became high again.. I ve checked for overflow of air and didn't find any. I ve checked the throttle linkage and the intake. I've tried several IACS , MAF and throttle position sensors. Tried to configure the ECU with T4 but it didn't show any problem. I don't know what to do next. I am close to the decision to burn this piece of sh*t...