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Daren
Dodge Dakota
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4/13/2006
09:58:53
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 Subject: 4.7L V8 Mileage Question
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I have a 2k Ext. Cab 4x4 4.7L V8 Truck. It's done this thing for a long time, and Im just wondering if its semi normal or if anyone knows what it might be.
When I leave my house in the morning and get right on the highway going 60-65, the engine runs at ~2200rpm for the first 5-10 minutes then it drop down to ~1900rpm. Is that normal? It doesn't seem to be related to temperature, as the temp is normal operating range and its still @2200. Its almost like its not shifting into overdrive right away but I know thats not the case, I've played around with that. I only get 12mpg according to the trucks computer when at 2200, then it goes up to 15mpg when the rpm's drop. I've moved since I noticed this a while back and now do almost all city driving. I do notice that whenever I get on the highway that it still does it sometimes. I'm guessing that they same affect is happening with my mileage in the city, crappy for the first 10 minutes or so. Because my drive time is now so short, I get 11mpg all the time, probably 50/50 city/open road.
I have 32 inch tires, and I know that hurts my mileage a lot. I don't really feel like taking the truck in, without diagnosing any possible problems myself. Anyone ever experience the same problem, or have any ideas as to what might cause it...if its even a "problem"?
thanks for the help
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jpkomm
Dodge Dakota
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4/13/2006
18:25:51
|  RE: 4.7L V8 Mileage Question
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I have the exact same year/engine truck as yourself. As best I can tell, what you are experiencing with the transmission is normal because it "learns" your driving habits. If you are doing a lot of stop and go or speed up and slow down styled driving, it may wait to go into overdrive (electronically adjust) till you go a relative distance at a fairly consistent speed. As always, if you want to best mileage, be as light on the gas pedal as possible and still maintain (as close as possible) that consistent speed.
Until your truck warms up, your mileage will generally be below par. However, your gas mileage rather sucks if you are only getting 15mpg. I get roughly 21mpg on flat highway. How many miles do you have on the truck? I just recently did the "TPS mod" on my truck because I think my TPS was acting up. I now seem to get better mileage and throttle response. I'm also hoping it fixes an idling issue I have in the mornings (running rich). My throttle position sensor was at .55vDC. From what I've read, it should be .7 to .75vDC. Of course, your TPS could also be inadvertently affecting your transmission shifting. Here is a link for a listing of tips and tricks for the Dakota given to me by a member of this site: www.geocities.com/dak2nv/perform.html
Good luck!
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Dark Jedi
Dodge Dakota
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4/13/2006
20:55:00
| RE: 4.7L V8 Mileage Question
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I have a 03 QC 4x4 I get 16 city and 24 HWY.
if your starting out on the hwy cold. your truck wont shift into OD intill its warm. also when the engine is cold it runs richer untill warm and then switched to the reg program.
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jasonsdakota
Dodge Dakota
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4/14/2006
00:29:28
| RE: 4.7L V8 Mileage Question
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actually daren, your truck is trying to help the environment among other factors. your truck IS in overdrive when you're crusing along at 2200 rpm, it's just that the torque convertor hasn't locked up. you'll probably notice if you lean into the gas or let off the gas the rpms will flucuate slightly. after 5 or 10 minutes of driving, your truck will warm up, and the torque convertor will lock up, causing your rpms at 60 mph to drop back down to 1900.
do not take it into the dealer. it is normal. the truck runs richer while it is warming up similar to the choke function on an old carburator. this combined with the higher rpms and parasatic loss of an unlocked torque convertor, is causing your instant mpg reading to be much lower when cold.
this "choke" feature is helping to warm up the catalitic convertor quicker and thereby reducing emissions. i have a 04 and a 00 dakota and can assure you that there is nothing to worry about.
jasonsdakota
04 ext cab 2wd 4.7 auto
ho cams
exhaust
4.10 gears
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Daren
Dodge Dakota
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4/14/2006
09:33:53
| RE: 4.7L V8 Mileage Question
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Thanks a lot for your help guys, I'll guess I just have to deal with the crappy gas mileage. The trucks got 88k on it, was planning on keeping it a few more years...
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jpkomm
Dodge Dakota
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4/14/2006
09:49:50
| RE: 4.7L V8 Mileage Question
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Wow, Jasonsdakota, you hit that right on the head. I knew there was an explanation behind it, but I only had a basic idea of what was going on. Bravo.
Still, Daren, your truck should NOT be getting 15mpg on the highway after it has warmed up. You may want to look into doing some maintenance on it to see if you can get it back up to par. Maybe a new TPS (can get one for $30 at Advance Autoparts) and clean your throttle body. Has the truck's front and rear differential fluid ever been changed? If it is old fluid, that can affect mileage (more friction = more work). I use Amsoil Syntheic Gear Lube in mine and it gave me an extra 1 or 2 more MPG along with getting rid of an irritating rear end chatter.
The service manual is also quite literal in saying that you need to change your spark plugs every 30k miles. The 4.7L just about eats them. Anyways, I'm sure there are more things you can do, but I can't think of them off-hand.
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Daren
Dodge Dakota
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4/14/2006
10:14:17
| RE: 4.7L V8 Mileage Question
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Theres got to be some reason why I get such bad mileage but I don't know if its even worth attempting to figure out. I suppose I could clean the TB, although I doubt that will make that big of difference. I changed the spark plugs about 20k ago, a mechanic friend of mine looked at them one day last year and said the engine looks like new. He replaced all the fluids in the truck at the time. When I first got the truck with ~40k, I remember getting 17mpg with a mix of city/highway driving. The 32" tires on it kill the mileage, I know that for sure. I put a soft tonneau cover on it last year but that didn't make a diff in mileage that I could tell.
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jpkomm
Dodge Dakota
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4/14/2006
14:50:34
| RE: 4.7L V8 Mileage Question
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I don't think your tires would effect it all that much. I have 31" tires on mine. Cleaning the throttle body could very well help revive your mileage. You'd be surprised what sort of crappy buildup you'll find in it at 88k miles. Here is a link with instructions how how to clean a 4.7L TB:
http://www.wjjeeps.com/service/tbody.htm
When you get time, try using a digital multimeter on your throttle position sensor and see what your voltage is. To do this, turn on the key (not the engine). Stick the positive proble through the weather protector on the TPS center wire at the connector. Have the negative probe attatched to the negative battery terminal. If it is measuring below .55vDC, I'd honestly consider either changing it or do the TPS mod.
After you clean your throttle body, you should definitely notice peppy throttle response. It may also not hurt to run a serious fuel system cleaner through your gas tank like Seafoam. I had some injectors that were a bit sticky from poor fuel quality and it straightened them out. Add it though only if you feel comfortable doing it.
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Dawooz
Dodge Dakota
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4/15/2006
18:03:03
| RE: 4.7L V8 Mileage Question
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You know I had this same problem about 3 years ago now. I took my "same truck by the way" in and the Dealer told me there was a Factory Recall that I had missed. After some tweaking with there computer and an upload to the Chip everything is smooth sailing now, but this was 3 years ago....
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Jecht
Dodge Dakota
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4/15/2006
20:08:43
| RE: 4.7L V8 Mileage Question
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Dawooz sounds liek the death flash to me. I got a superchip programmer and seems to help alot on my truck.
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METALHEAD
Dodge Dakota
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4/16/2006
01:47:57
| RE: 4.7L V8 Mileage Question
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Well I am unsure about the little v8 but is the smaller one like the 318? Can he look inside the intake plenum to see if there is oil hinting to a vacuume leak? I just had some running problems with mine but I had everything from the distributor to the intake and timing. Haven't gotten it together yet. will be totally done come tuesday when the dist gets here though hehe.
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shane
Dodge Dakota
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5/22/2006
20:30:55
|  RE: 4.7L V8 Mileage Question
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I have a 2006 Dakota with the 4.7 . I get 15 mpg on the hwy.
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Pugs
Dodge Dakota
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5/23/2006
22:50:20
| RE: 4.7L V8 Mileage Question
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I have a 2002 4.7 (with 5-speed) 3.55 gears.
I live in Canada so have 120K KM's and no major maintenance done (plugs changed at 60K).
My mileage is about 11.33L/100KM (.1133L/KM) on a good day on the highway. What's that convert to into MPG like you guys are talking above? Am I good or bad? One thing to keep in mind is that the faster you go on the highway, the crappier your mileage will be. I find about 115KM/h is the most efficient speed for me. If I cruise at like 130, then my mileage goes to about 13-14L/100KM.
Thx
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JerryM
Dodge Dakota
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5/24/2006
08:51:49
| RE: 4.7L V8 Mileage Question
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I have a 2000 4.7 liter with 48K on it and too only get about 13-15 mpg driving around town.
I just used Seafoam in the gas tank and throttle body, hope it helps. I also took out my K&N filter and put my stock filter back in. Some feel that the K&N filter creates more air flow which results in more fuel. Result less mpg but more power I guess.
I have not tested my TPS but should probably give that a check.
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Kowalski
GenIII
5/24/2006
13:05:14
| RE: 4.7L V8 Mileage Question
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My 4.7 (which is nothing like the 318, metal head) has always been around 15 mpg since new. I don't think that should be considered bad milage for a truck of its capabilities.
Daren - You could be getting worse milage due to the 32's; you could also be getting the wrong info if you aren't adjusting for the extra distance the 32's cover per revolution compared to the stock size...
Lead, follow, or get out of the way
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choochoo
Dodge Dakota
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5/24/2006
22:38:58
| RE: 4.7L V8 Mileage Question
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2004 QC 4.7 5spd auto 3.55 4x4
Leer cap K&N drop-in
stock tires @ 38 psi
Best: 21 mpg hiway
not much worse in city
Very few jack-rabbit starts - just enough for the occasional smile!
20k original Champion plugs
Castrol GTX 5W30 engine oil
semi-synthetic in both diffs
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pugs
Dodge Dakota
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5/25/2006
22:52:43
| RE: 4.7L V8 Mileage Question
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Does anyone know what the conversion is for Metric gas mileage measure (X L/100KM) to turn it into M / Gallon?
I'm about 11.33 L/100KM
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choochoo
Dodge Dakota
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5/25/2006
23:57:22
| RE: 4.7L V8 Mileage Question
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Hey pugs: There is a way. I will give you the math, maybe you can figure out a chart for quick reference.
First divide the # liters by 4.54 for Imperial gallons or 3.8 for U.S. gallons
Then change the km into miles = about 62.
Now divide 62 by the first number you got.
Example: 16 liters/100 km
16/4.54=3.52
62/3.52=17.6 mpg Imp.
OR 16/3.8=4.2
62/4.2=14.8 mpg U.S.
I have the benefit of a console readout in my Dak with liters/100km and U.S. mpg
I have never liked metric, even though I live in Canada, so I leave my readout in U.S. mpg and add 3.2 mpg for Imp.mpg.
Have also checked the mpg with the math and as posted earlier am happy with my mpg.
Actually if it was up to me I would ban metric, but it will never be up to me!
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Mr.Sleepy
Dodge Dakota
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5/26/2006
15:54:32
| RE: 4.7L V8 Mileage Question
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Daren,
I don't know for certain, but I've heard that when you put bigger tires on a truck, you need to reprogram the computer for oversized tires. Your bad mileage is no doubt a mix between the extremely heavy oversized tires, probably higher gear ratio, and having a 4x4 transfer case. Generally you aren't building a commuter mobile when you put 30 inch tires on a truck.
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Daren
Dodge Dakota
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5/26/2006
18:47:20
| RE: 4.7L V8 Mileage Question
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I dont think it makes too big of a difference as far as the electronics in the truck. Its only one inch difference so I don't think reprogramming the computer is necessary. At 64mph on my gps, my trucks speedo shows about 60 for reference. I've never really calculated the difference that the mpg's on the computer are showing me.
I know the truck isn't going to get me the best mileage, I got the tires before the crazy gas prices though. I don't drive any huge differences anymore so its not a big deal. I was just concerned about the health of the truck with that whole initial rpm issue mentioned in the original post.
Thanks for the tips though everyone, I recently took the throttle body off and cleaned it out, it was black but there wasn't too much buildup. I ran a can of seafoam through it as well, I think it helped the mileage a bit, not much...half to one mpg maybe. I've used seafoam in boat and other smaller engines in the past with great success. I just never thought of it in the trucks.
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Kowalski
GenIII
5/27/2006
08:23:36
|  RE: 4.7L V8 Mileage Question
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You are definitely getting innacurate results for mileage then if you don't account for the fact that your larger tires are covering more than a mile for each mile registered. You can't do a proper comparison without accounting for that.
Lead, follow, or get out of the way
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