4.0 V6 year 2000 Explorer (UK)
In certain condidtions my Explorer suffers from 'sluggish' accelleration
which can be quite alarming (and dangerous) when pulling out into traffic
and nothing much happens when I stomp on the gas...
From a standing start everything seems fairly normal -  in comparison to the
'98 Ex I had before this one, anyway.
The problem arises from a low speed rolling start. A typical scenario is in
a line of traffic at a level or slightly downhill junction or intersection.
Traffic enters the main road fairly regularly so the line keeps moving at
approx 5mph. I get to the head of the line still trundling along at less
than 10mph, see a gap in the traffic and stomp on the gas expecting to
unleash the 200+ horses hiding under the hood. Not much happens! The revs go
up a bit and there is some acceleration and I can hear the motor 'trying'
and sense a small amount of torque converter slip. The impression at this
point is like being in a high gear (I suspect it's 3rd). Eventually after
what seems like an age but is probably 5 or 6 seconds, the truck 'realises'
that I want it to 'go' and it changes down a gear and starts to accelerate
and then changes down another gear and really takes off like I wanted it to
do in the first place.

OK, that was problem #1

Problem #2 may well be linked. When maintaining a steady speed (any speed as
long as it's constant) between approx 50mph and 80mph I get an intermittent
misfire. It's like a momentary cut out, not like a single sparkplug going
off for a moment. I suspect something like a throttle position sensor might
be at fault as the feeling is pretty much like when the throttle position
sensor went bad on a car I had a few years ago.

Has anybody got any idea where I should start looking? (apart from in the
rear view mirror when I've just pulled into traffic...) Oh! and don't
suggest booking it into a Ford dealer! Ford dealers here in the UK know
absolutely nothing about Explorers :(

TIA
Simon H