Thought I'd add my issue to the list:
3.0, longblock replacement a few months ago

-When new engine went in, noticed warmed up idle was 700 (800 prior)
-Had to plenum and replace a bad valve cover gasket -- no change
-Replaced throttle cable (after sticking at 70 MPH on the highway!), and then had the oscillating idle, which is like this:

-once warmed up (about 10 mins), starts to oscillate and then may stall out
-if in drive, idling at stop, at worst
-no effect on or off brake
-in neutral, idle speed goes up from 700 to 800, eventually starts to oscillate, but takes longer/less bad them when in drive
-after 5-10 more minutes gets better

-replaced distributor cap & wires (a short at center post in distributor)
-no vacuum leak found (even with going over engine with propane tank listening for idle change)
-Pulled CEL codes → nothing
-Pulled ECU fuse → nothing
-thinking it isn't brake booster given lack of effect of braking
-so most likely the cold start valve?

Replaced the cold start valve. Minimal difference (maybe a hair better)

Now have noticed that seems some link to headlights being on (i.e. turn headlights off, idle gets mostly better) … and come to think of it this happens much less during daytime. With headlights on and things acting up, voltmeter reads mostly 12 (instead of 14) tho not consistently so.

WTF? Some link to alternator going (150,000 miles likely needs new brushes)? Or TPS (given timing with throttle cable replacement)?

Thanks

 

TPS may need adjusting. Idle - E1 contact must be closed when the throttle plate is closed.

 

Will try with
http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml

 

Checked Dashpot: seems OK though filter dirty -> all cleaned
Idle screw seems right
But what is this (over the TPS)?

 

The dashpot

 

No, actually it's not. The dashpot sits in front of the throttle body, adjacent to the idle adjuster screww thing. It's plastic and pulls apart (so you can access the filter)...

 

I had a similar problem for a while then I eventually kept blowing the efi fuse everytime I tried to start it. My problem was an easy fix.

My o2 sensor wire Under the drivers side door was touching the exhaust. I pulled it back and braced it so it couldn't fall back down on it and that solved all the problems.

It may not be what's causing your problem but it only takes a second to check.