Hi guys, just a little tip for anyone running a vehicle with a 3.9 EFi "hotwire" system.
For a while now my dual fuel Rangie has had a bit of an erratic tick-over, then the other day, after it had stood for a week, I started it up and it rev'd to about 2500 RPM and wouldn't drop back, whatever the throttle (problem the same on GAS and petrol)
Anyway after a bit of messing about I found that if I pulled the "throttle butterfly bypass" hose off and bunged it up with a large bolt the engine ran fine.
On further investigation I removed the stepper motor unit that controls the airflow through the hose and cleaned the actuating arm, it was totally gunked up with nasty brown cack. Now it works fine. (no need for the bolt anymore!)
So if you get a similar problem that might just be the solution.