I have had this happens once or twice, and have had the idle air control out and cleaned it. It seems better, but then the weather is warmer. This is a stepper motor on the 3.9EFi, probably the same for the 3.5. It only affects idle. The air flow meter is a hot wire system on the 3.9, but maybe an earlier flap type on the 3.5 Efi - its something I haven't had apart. I don't think it will be that, as it affects the entire throttle range - but it may be that the flap type has a special way of failing that does this.

Of course it is important that there isn't some silly reason that the throttle is held open, because that will cause the engine to rev no matter what the other controls are up to. There is a conventional throttle butterfly in the inlet, and if the throttle stop is wrong, or the cable is tight, or the outer cable has popped out of its seating, then maybe its something like that. Best to check that first as fixing it is easy and cheap.

Steve

There's a lot of talk these days about green transport. Well, I am ahead of the game, I already have green transport ... British racing green.