"Sluggish" 4.0 Explorer

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

Prob #1 sounds like transmission. What happens when you shift manually,
i.e. at the stop be un "L", then looking at the rpms and engine sound
shift to "2", and ..... you get he idea.

Prob #2 is your "ck engine" light on? Look at your plugs and wires.

"mike" > wrote in message
oups.com...
> Prob #1 sounds like transmission. What happens when you shift manually,
> i.e. at the stop be un "L", then looking at the rpms and engine sound
> shift to "2", and ..... you get he idea.
>
> Prob #2 is your "ck engine" light on? Look at your plugs and wires.
>

Thanks for the reply.
No CEL. Plugs were replaced at 40k miles - no difference. Plug wires look
and 'seem' OK.
I'll try the 'manual' method tomorrow, but it's not gonna be a true test as
on the 5 speed auto box position '1' = 1st gear, pos '2' = 3rd, 'D' = 1,2,3
or 4 (or 5)
I'd be interested to know what system has replaced the kickdown mechanism on
earlier auto trannys? I think the truck 'doesn't realise' that I want it to
GO when I stomp on the gas - it seems to just wait around for the gearbox to
go through it's torque sensing routine and shift down the gears one by one.
If I 'stomp on the gas' at , say, 30 or 40mph the truck behaves just like
you'd expect and it will accelerate hard up to 100mph without any problems
(apart from the traffic cops) - it's just the take off from a low speed
rolling 'start' that's an issue.

Cheers
Simon H

Electronic transmissions don't need 'kickdown', modulators, or any other
round-about tricks to sense throttle input and engine load. Instead of
having their own hydraulic 'brain', they are controlled directly by the PCM
(engine computer). That box knows as much as can be known about what your
engine is doing, how fast you are moving, what the temperature on the moon
is at the moment, etc, etc. Well, a bit of exaggeration, but you got the
idea. All that works as long as the sensors are functioning correctly. But
typically when they don't, the CEL turns on.

The sluggish acceleration sounds like a transmission problem, but it could
easily be ignition. If this vehicle still has ignition wires (not
coil-on-plug) I would start there. They are notoriously difficult to test
without an oscilloscope and known to fail, sometimes very early. It's
probably a safe bet to replace them on 6 year old vehicle, just as a
precaution. Taking a look at the plugs couldn't hurt either.

"mike" > wrote in message
oups.com...
>I'd be interested to know what system has replaced the kickdown mechanism
on
>earlier auto trannys? I think the truck 'doesn't realise' that I want it to

"Simon H" > wrote in message
...
> 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.

Since you don't seem to say what you've checked besides the throttle
position sensor let me ask: did you check the air filter and fuel filter?
Have you checked the mass airflow sensor? What about the spark plug wires?
To me it sounds like a transmission problem but I'd check those things
first. Check the vacuum lines too.

>
> 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
>
>

5 or 6 years ago Ford issued an update to the PCM in my '97 4.0L SOHC
Explorer for the same symtoms you have described. Per Ford, the issue could
be experienced when coming to a stop when traveling at a speed of 45-55 MPH.
If you rapidly step on the gas, the transmission can get stuck in 3rd gear
causing a "percieved lack of acceleration". Well I wasn't percieving
anything, it left me stranded in the middle of the intersection more times
than I can remember while I waited for normal acceleration to resume. Once
they updated my PCM though I have not experienced the issue since.

Alpine

"Simon H" > wrote in message
...
> 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
>
>