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03TroutTruck
Dodge Dakota
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3/24/2005
13:19:26
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 Subject: Crappy Towing Mileage?
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My Dakota is an '03 Quad Cab with 3.9L engine and 5 spd manual tranny, and the truck has a topper. When I'm towing my boat (total weight of boat & trailer is ~1,000 lbs) at 65-70 mph on the highway, I get at best about 13 mpg. Without the boat, my mpg is 1 or maybe 2 mpg better, in both cases with myself and two passengers. Only once have I approached the advertised 19 highway mpg with this vehicle, that was with a light load and avg speed closer to 50 mph. I'm taching only a little over 2k rpm at 75 mph in 5th gear, and have to downshift frequently to 4th to negotiate hills. Anybody else getting better mpg in similar conditions? Should I quit even using 5th gear while towing? I was expecting better mileage with this engine/tranny package. Were my expectations out of whack? or is there something wrong with my truck? I had a loud whistle @ 2,000 rpm from my engine during the only real cold spell we had this winter and suspected a vacuum leak, but dealer said they could not find any vacuum leak. Whistling quit since air temp rose back above single digits. Any answers/suggestions greatly appreciated.
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93dak4x4
Dodge Dakota
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3/24/2005
13:54:33
|  RE: Crappy Towing Mileage?
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your truck is a heavy quad cab and you are pulling with a 3.9. the truck is underpowered to begin with, i would expect you to get 13-15 towing at 70. at 75 i only get about 17-18 mpg with a 93 cc 4x4. so dont feel like you are in a place nobody else has been.
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Dan M
Dodge Dakota
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3/24/2005
16:17:00
| RE: Crappy Towing Mileage?
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I don't think it's just the weight. I have a '95 CC 4x4 auto with 3.9, I get 17 combined city/highway and 21-22 driving 70-75 on the highway with a tonneau.
I pulled a 12x6 uhaul trailer helping my sister-in-law move and driving 60 I got 14mpg. This was state roads, with alot of flat roads and a few hills and curves - about 190 mile trip. I know the trailer and it's contents weighed more than 1,000 lbs, I would guess around 3500-4000 lbs.
- Dan M
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um
Dodge Dakota
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3/24/2005
16:21:28
| RE: Crappy Towing Mileage?
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your poor mileage could be caused a lot of things but it would be worth checking your injector sync it should be +3 degees
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jared
Dodge Dakota
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3/24/2005
17:15:59
| RE: Crappy Towing Mileage?
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I tow a small pop-up camper with my 2003 club cab. It has the 3.9 with a 5 spd with the 3.55 axl ratio. When it was bone stock I got about 15 - 16 mpg towing with it. The trailer, gear, and firewood weigh about 2000 lbs. Last summer, after adding a cold air intake and a flowmaster muffler, I got just under 18 mpg towing. There was not any difference in driving conditions. It was the same trip over the same roads.
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03TroutTruck
Dodge Dakota
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3/24/2005
18:08:18
| RE: Crappy Towing Mileage?
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What is injector sync? How do I check it?
thanks to all who are replying, and keep the advice coming.
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RPRacing
Dodge Dakota
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3/24/2005
20:11:23
| RE: Crappy Towing Mileage?
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I got 13mpg with my regcab 5 spd 3.9 towing a 6X12 enclosed doing ave 85mph. :) Then again I have a shell on the back so the air doesnt hit teh front of the trailer full force.
(BTW its not recommended to drive over 70 with any trailer.:D )
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Dan M
Dodge Dakota
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3/24/2005
22:20:40
| RE: Crappy Towing Mileage?
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I think the 6x12 even has a label on it about max speed being 45 mph, at least, that is what I remember. :)
- Dan M
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93dak4x4
Dodge Dakota
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3/24/2005
23:44:37
| RE: Crappy Towing Mileage?
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Injector Sync:
http://www.dodgedakota.net/boards/v6/11574.html
I reset my injector sync as per the post listed and gained 3mpg
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Mopar318
Dodge Dakota
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3/25/2005
16:22:25
| RE: Crappy Towing Mileage?
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I have a 96 318 4X2, Auto. I get 13 going about 65 on they highway. That is with out a trailer so you should be glad you get that. Plus I have the lightest model. RC shortbed 2 wheel drive.
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vern
Dodge Dakota
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3/25/2005
16:40:23
| RE: Crappy Towing Mileage?
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if you get a chance check your speed o meter against the measured mile to see if its right.
my truck is 1/10 of a mile slow,so in a 100mi on the meter, i,m going 110mi,its not much but it does make a differance in the mileage you think your getting.
larger tires will do this
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J and J Auto
GenII
3/26/2005
03:44:40
| RE: Crappy Towing Mileage?
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Things that effect gas mileage
Injector sync
dirty air filter(cold air system or K&N drop in)
bad o2
lazy map sensor
engine temp sensor more than +-15 degrees off
IAT +- 15 off
bad cap rotor wires or plugs(incorrect heat range
or gap .040 to .045
vac leak normal 18.5 to 18.9 at idle
leaky pletium gasket
low fuel presure 40 to 50 psi normal
leaky injector (or dirty)
92 to 95 bad egr
tight ujoints or a break draging
a heavy foot
just some things that need to be checked to get
optimal gas mileage
The Jet stage 2 chips show an increase of
1 to 3mpg on every truck we have put them on but
everything was checked befor instalation and fixed
at the time thay were installed the more mods the
better the resaults these chips can be run with
a stock setup most on reg fuel some had to goto
89oct but very few even with the crank sensor mod
adding more timming
The mods jet tells you about are recomended but
not nessasary
Doing the crank sensor mod will also help low end
and gas mileage
Mods to my stock 92 motor in my 95 4X4 getting
23mpg in 20 to 40 degree weather over 100,000
miles on this motor
Ram air
K&N filter 14X3 with exstream top
48mm F&B
gasket matched intake stock runner length
19#fms injectors
sync +3
heads port clean up and polish very mild porting
just a good clean up
crank sensor 4 degree advance to check base
timming pull fuel pump relay crank over with
inductive timming light and you will see where
base timming is at
95 stock comp jet 2 chip
stock ign with napa brass cap MSD 8.5 wires
Halo H9a plugs none adjustible gap at .045
JBA headers carsound high flow dynomax 11748
single 2.5 tail
elect fan permacool 2950cfm
1.7 harland sharp roller rockers
42RH with TCI TransScat shift kit 3.55 gears
1500rpm stall on converter
PVI injection system
running reg gas engine temp 185
1995 sport 4X4 reg cab short box with tonna cover
the tonno covers will help 1 to 2 mpg less drag
All Amsoil syn except motor running royal purple
10w30
Royal Purple is dyno proven 3 to 5% hp and torque
increase and 3 to 5% mileage increase this is the
only oil that can prove its claims on a dyno and
it does do what they say
Think I got everything listed
Larry
J&J Auto
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03TroutTruck
Dodge Dakota
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3/27/2005
16:29:08
|  RE: Crappy Towing Mileage?
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Message:
Thanks for all the tips, especially Larry. I got started with the wrench turning today. It's been a long time since I've played around under a hood. Today I took care of the injector sync and installed new cap and rotor. What a pain it was messing with the distributor. Larry, I don't know about the older Daks, but on mine there's absolutely no way to look straight down at the rotor, it's blocked by the cowl. I went and bought a little hand mirror to try and get a better look, felt like a dentist working on somebody's back molar. Anyway, I did do some adjusting, and on my short test drive, it did seem to have a slight gain in bottom end torque. Is there a way to actually measure the injector sync (electronically or otherwise), or is eye-balling it the only way to go? In any case, I've also ordered a 360 Air Intakez CAI system via the group buy. I should be able to get a longer test drive later this week or next weekend and will do a mileage test at the same time. I'll also keep putzing on it, working on some of the other issues mentioned in this thread and other similar ones. How do I locate the crank shaft sensor? Is it located on the engine block or bellhousing? thanks tons.
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Dex
Dodge Dakota
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3/27/2005
18:55:11
| RE: Crappy Towing Mileage?
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J and J Auto
Where are you located?
If you were in Ga. I would stop by for some mods.
I can change spark plugs but not much else.
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gen1dak
Dodge Dakota
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3/27/2005
23:17:55
| RE: Crappy Towing Mileage?
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I don't know this to still be the case, but those highway EPA ratings are probably still based on a cruising speed of 55 mph with no real load.
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FloriDak
Dodge Dakota
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3/30/2005
13:22:02
| RE: Crappy Towing Mileage?
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Message:
yea, a tune-up is a good idea for better mileage all around... even though it's only about 1000 lbs, the trailer adds wind resistance, which will reduce mileage a bit too.
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xmr
GenIII
3/30/2005
15:28:33
| RE: Crappy Towing Mileage?
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Message:
03trouttruck: the crank position sensor is on the bell housing on the passenger side just below the head. On your truck and mine the best way to reach it is to take off the right front tire and the plastic splash shield then you can get to it. some where there is a good pictorial how to on this. It is well worth the effort.
Dex: you are out of luck Larry is in Wisconsin
'98 cc auto /Home brew cold air with K&N,Dynomax, Superchip Tuner, 1.7 RR,, F&B tb. NAPA cap and rotor, 3923 plugs,tps mod,relocated & switchable iat, 180 t'stat, Crankshaft sensor mod.,PVI,Ported and Polished manifold, bosch injectors,Black Magic Elec Fan, msd wiires
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J and J Auto
GenII
4/02/2005
04:28:22
| RE: Crappy Towing Mileage?
IP: Logged
Message:
The injector sync can be checked by mopar but most
techs will only set it from -6 to 0 and not
behond to the + side
Also a good scanner like the snapon MT2500 I ran
mine over one fine day and did not want to spend
$3000 for a new one so I went with the Auto Xray
scanners one for obd1 $150 one obd2 $200
do the crank mod it will help a lot if you get
any ping just drop 1 heat range on your plugs or
god forbid with the gas prices go up 1 range on
the fuel
elect fan and a tonno cover will also help a lot
remove the big clutch fan
Larry
J&J Auto
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03TroutTruck
Dodge Dakota
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4/06/2005
00:04:46
| RE: Crappy Towing Mileage?
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Message:
Initial results mixed. Only in-town tank with injector sync mod, new rotor and cap resulted in 13.5 mpg, an increase of ~1.5 mpg city. Two 150 mile boat-towing trips over weekend netted a slight loss in mpg, down to 11.7 mpg @ 75 mph with boat in tow.
360 Air-Intakez Power Shot CAI unit installed today. Air horn needed some work to make it fit, but 45 minutes with hack saw, file, and sandpaper, and the fit is now passable, if not good. Should have more data with that upgrade by end of weekend. Picked up a used throttle body on ebay that I thought I'd try to clean up and install. Also picked up a 180 deg thermostat. I'll keep you posted....
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