The only experience I've had with a pre-mag 3.9 was my
Dad's 1987 Dakota. It was sufficient,I thought. ran
pretty good. Pulled hills good. ran really smooth and
quiet. It's only been the Magnum V6's I've had issues
with. The truck I was talking about is a 2003. Tell ya
what. Here's a bit of history on my experience with
Magnum 3.9's:
In 1999,I bought my first brand-new vehicle,a 99
Dakota Sport 4X4 RC 3.9 automatic with 3.92 gears. I
thought it ran okay,but I just really liked the truck
overall,Intense Blue and nice factory stereo,and the
nice interior that used to be available in Dakotas.
But shortly after I got it (you'd have to dig into the
archives to see when it happened,I believe at about
8,000 miles) it started running crappy at random,and
you could smell the cat a lot of the time. I took it
back to the dealer,and "could not duplicate" was the
order of the day. Then they gave me a co-pilot device
to drive around with,where I could hit a button and
record trouble events,but after two or three times
with the unit not working or them failing to get it to
download to their computer,
I gave up on that. Then one time I let the service
manager drive it while I rode with him,and he said he
thought it seemed like it wasn't doing well,and they
changed the cat. Still didn't get it. At that point,I
decided the 3.9 engine must just have varying levels
of performance. I had read online about other people
not happy with that engine on their Daks. But it still
seemed really funny that sometimes I could cruise
uphill at 65 mph with the air on and it did great.
Other times it struggled up the same hill without the
air running. Regardless,I decided to live with
it,thinking I'd get the same truck with a 318 when I
could.
So...in 2000-01 I started looking again. Looked for
quite a while. By the time I found a replica of my 99
(same options,gearing,etc.),the 318 was no more. I got
an '01 with the 4.7,automatic 4X4 RC with 3.92 gears.
Still have it. It runs great. But my 3.9 story doesn't
end there!
August a year ago,I was driving a rattletrap Chevy
workvan,and my boss said I could look around for
something else. Eventually he bought an '03 Dak CC 2WD
auto with 3.9 that he had spotted on a car lot with
19,000 miles on the clock. I test-drove it,and
recommended it to him. I hesitated (no pun intended)
on recommending the truck due to the engine,but I
figured my 3.9 issue must have been a fluke.
Well,like my '99,this truck seemed to be okay for a
while. But now it's running as bad or worse than my
old Dak did. Like Don said,as I approach a slope I
kick it down early,and it normally falls all over
itself. I then keep the pedal down almost to WOT,and
you can feel a jerkiness to the "pull" of the
motor,like it's sputtering or slipping,and the tach
kinda hangs for a split-second in different spots as
it climbs. Sometimes it's so bad,I have to just mash
the pedal down and keep it there. I back off when the
engine sounds like it's going to come apart,or to let
it upshift.
There are times though,that I could describe as
"glimpses of glory". Like yesterday,I drove up a
fairly steep hill about half a mile long,and with the
AC running it maintained 50 easily. No
jerkiness,nothing. Smooth. Didn't have to kick it down
into passing gear to go up the hill. I've also had it
easily maintain 65 mph on those same highway slopes
with the air on. But those times are rare. I don't get
it. I've done plugs and wires,PCV valve,checked the
distributor cap and rotor (cleaned,but nothing
wrong),and changed the MAP sensor. Switched gas
stations,tried fuel injector cleaner. Now I'm almost
back to the point where I'm believing there's
something inherent with the 3.9,or maybe PCM
programming,that causes performance to change a lot
for no apparent reason. Maybe others have different
experiences,but my only good memory of a 3.9 Dak was
not a Magnum.
Steve P.
- Don Rey <radon220@gmail.com> wrote:
>
> > P.S. I drove the work Dak (which has a
> badly-running
> > 3.9 in it) all day,and I wish I could describe the
> > difference between the two trucks. I'd like to
> have
> > the 3.9 dynoed. It would be about 90 RWHP.
>
> What year is the work truck? 3.9 Magnum? My Dak had
> the premag 3.9
> before my swap and I definitley know what you mean.
> What a pig. If I
> didn't hit an incline at 70mph+ I would lose speed
> climbing with the
> pedal to the floor... on bad hills, I'd be doing 40
> by the time I
> reached the top. Like you said, dropping to 3rd
> (before the
> transmission decided it was time) would help a
> little. I could do a
> pegleg burnout in reverse though.
>
> Don in CT
> 89 DakVert 5.2 5spd 4x4
> 74 Dart Sport 340
>
>
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