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2kdak
Dodge Dakota
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2/08/2004
20:49:13
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 Subject: declining gas mileage 4.7l
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I bought my Dakota 2 years ago, it had 36k miles at the time. I would average 15-17 mpg highway, 12-14 city. I have installed a drop in k&n filter and recently had to replace stock muffler. I went with a flowmaster. Currently it has 98k miles and I average 10-13 highway and city. Runs and sounds great but the dropping mpg has got me worried. I am not mechanically inclined and am open to any suggestions.
2000 4.7l sport 4x4 quad cab
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fastyz400
Dodge Dakota
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2/08/2004
22:00:50
| RE: declining gas mileage 4.7l
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2kdak,
Change your plugs and wires, i don't think the 4.7 has a rotor and cap.
another thing is it's time for a new O2 sensor. Just change the one before the cat, that's the one that sends all the info to the computer for timing and fuel adjustments.
Just did mine at 60k, what a difference.
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2kdak
Dodge Dakota
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2/08/2004
22:21:05
| RE: declining gas mileage 4.7l
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thanks for suggestions I had the plugs and wires changed but thinking of switching to Autolites #3923's. I will replace o2 sensor. What is general cost of 1?
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CThomp
*GenIII*
2/09/2004
08:28:48
| RE: declining gas mileage 4.7l
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You can get all of these after market. Look into the possiblity of your cat being clogged as well. You could switch to a free-flow cat for less than $100 and you'll see some improvements in performance. I've got a carsound cat on mine. There are several sites that sell them. v8performance.com is one of them.
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01Motorsport
Dodge Dakota
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2/09/2004
09:06:15
| RE: declining gas mileage 4.7l
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Take your truck to a Dodge dealer to check the O2 sensors on a scope first, or a shop that has a scope. If a code isn't showing on the dash, they're probably okay. Try some easy things in your mpg search first, like the plugs (no wires,cap or rotor on 4.7), air filter, PCV valve, fuel filter, and even tire pressure. Try a bottle of fuel injector cleaner in the tank, and carb spray in the throttle body. Gradual decline of mpg usually is just maintenance needs.
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JES
Dodge Dakota
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2/09/2004
09:10:15
| RE: declining gas mileage 4.7l
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01Motorsport -- Fuel Filter? .... I searched around under my truck for a fuel filter (02 QC 4.7L Auto AWD) and found nothing. I just assumed it was in the tank and "installed for life". Is there a filter somewhere on these trucks that can be changed out?
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TexasTodd
Dodge Dakota
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2/09/2004
10:14:13
|  RE: declining gas mileage 4.7l
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2kDak,
If someone told you they replaced your plug wires...I think they may have ripped you off.
The 4.7, does NOT have the standard, thick plug wires! It's coil on plug, 8 coils, small ones, and the wires should never need replacing.
Todd
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fastyz400
Dodge Dakota
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2/09/2004
11:33:47
| RE: declining gas mileage 4.7l
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2kDak,
I bought my O2 sensor at Checkers auto, $79.00. Then, i had to save the old connection from my old O2 sensor. Soldered all the wires together then shrink wraped.
I don't know where the O2 sensor is on the 4.7, i have a 2000 5.9. It was right below the passenger floor board. Took some, rust free upper, sprayed it on, let it sit for 30 min. Went back and wrenched it out.
My mileage increased like 2-3 mpg.
Keep in mind, that an O2 sensor doesn't have to fail to give you poor fuel mileage. Age and buildup, usually cause your O2 sensor to have false readings. That's what gives you the crapy gas mileage.
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Tnjones
Dodge Dakota
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2/09/2004
17:50:47
| RE: declining gas mileage 4.7l
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Have you considered the 'Vrrooom' factor? That's where your truck now goes 'Vroom' since the muffler swap and you like the sound so you go 'Vroom' a lot and so your gas milage dropped a little. Pretty common with this mod actually. Ask the guy who did your muffler.
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WINTER
Dodge Dakota
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2/10/2004
19:49:53
| RE: declining gas mileage 4.7l
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These 4.7's typically loose 2-3mpg during the winter months. Wait until spring gets here before you throw a lot of money away. The plugs probably do need replacing since it has 98,000 miles on it. If you want a gas mileage increase, don't put the 3923's in there. They are colder than the originals. That will result in lower fuel mileage. Get the Bosch Platnims if you want to see an improvement in fuel mileage. You might just file and regap your existing plugs. You might consider a new thermostat. The original should be OK, but with 98K on her it might not be letting the engine get all the way up to temp. This will drastically reduce your fuel mileage as well as cause excess condensation in the block. I wouldn't jump up and spend a lot of money for a couple of more months. You might be suprised the first tank of gas you run on a 70 degree day. That would also indicate a new stat is needed.
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Demon
Dodge Dakota
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2/11/2004
05:40:03
| RE: declining gas mileage 4.7l
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At 98K I would think you just need a tune up. At 70K and mine is due, noticing a slight drop in performance.
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01Motorsport
Dodge Dakota
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2/11/2004
09:59:35
| RE: declining gas mileage 4.7l
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You're right, JES, the fuel filter is built in with the pressure regulator on top of the fuel tank. Not routinely serviced.
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2kdak
Dodge Dakota
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2/11/2004
15:41:17
| RE: declining gas mileage 4.7l
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I did have it tuned a couple months ago and wires were not changed. Didn't mean to say that force of habit 8) I keek my tires at high PSI 50 PSI at cold temp. I think it is more a matter of 02 sensure, clogger cat or the like. I will start with cheap fixes and go from there. thanks again for your thoughts.
2000 4.7l sport 4x4 QC auto 3.55g
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fastyz400
Dodge Dakota
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2/11/2004
17:31:12
| RE: declining gas mileage 4.7l
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Try some fuel system cleaner, it will help clean out the deposits inside your engine's combustion chamber.
I did one bottle after the next. And it did help. Noticed the engine to be more responsive.
Have you tried different gas stations?
Out here in Arizona, i have tried, Mobile, Texaco, Arco, your cheapy gas at Fry's, and found Cheveron to be the best for my 5.9.
It ran smoother and just seems to run better.
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2kdak
Dodge Dakota
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2/11/2004
18:09:38
| RE: declining gas mileage 4.7l
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I have run Injector cleaner through it, and after several tanks it did not make any noticable differance but I continue to use it about every 4 tanks or so. Also I have been looking at different post about what the best plugs are for the 4.7l and still get uncertain answers. Has anyone used the +4 plats from Bosch? Should I stick with stock #'s plugs, and if stock what brand is best? Also for free flowing cat do you just replace first cat or all three?
2000 sport 4x4 QC auto 3.55g
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fastyz400
Dodge Dakota
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2/12/2004
02:50:04
| RE: declining gas mileage 4.7l
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You should always replace the o2 sensors before the cat. The ones before the cat are used by the engine to adjust timing and fuel.
The one after the cat is to see, if the cat is effective. It really doesn't do much.
Heck they even make, dummy connectors for the back one, this is to fake the computer in thinking that it's there. A lot of tuners use this to fake the computer out. Thus, allowing more emmisions to past without setting off an engine light.
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TexasTodd
Dodge Dakota
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2/12/2004
11:25:44
| RE: declining gas mileage 4.7l
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2kdak,
What would you tune up on a 4.7?
Electronic ignition-you can't even adjust the timing! Change the plugs maybe-which is rarely needed anyway.
I hope you find the culprit, let us know if you find anything that objectively makes a difference in the MPG on your 4.7.
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2kdak
Dodge Dakota
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2/12/2004
12:07:04
| RE: declining gas mileage 4.7l
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TexasTodd- I took it to a mechanic to have it tuned at around 65k miles, had them check brakes aswell. I think all that they did as far as tuning it was change the plugs. It wasn't that exspensive, can't remember what the exact cost was. Undey $50.00 I think. And I will let you know of any improvements to MPG. Have been ckecking on o2 sensors to find best prices. Thanks for continued advice.
2ooo 4x4 sport 4.7l QC auto 3.55g
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fastyz400
Dodge Dakota
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2/12/2004
15:57:06
|  RE: declining gas mileage 4.7l
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goto www.boschusa.com
You can find the O2 sensor part numbers for your 4.7.
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Jeeper
Dodge Dakota
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2/19/2004
01:22:59
| RE: declining gas mileage 4.7l
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I used the Bosch +4's and was not happy at all with them. Gas mileage and power were both noticably down. When I took them back to return them the guy said "yeh, we don't sell many of these anymore because the 4 ground electrodes shroud the spark, slowing combustion, reducing power and mileage."
I switched to a standard copper plug. NGK splitfire ZFR6F-11. BIG improvement in power and mileage.
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Red4x4Dak
GenIII
2/22/2004
22:20:07
| RE: declining gas mileage 4.7l
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i have a 2000 with the 4.7 and i have noticed that my truck as well gets bad mileage. was looking for plugs but i see that the NGK mentioned above are about $11 each. thats alot for plugs. if they will get me better gas mileage then i guess that they will be worth it. i have one other question while i am at it. does anyone with the 4.7 have a ticking sound coming from the valve train. i have only had the truck for about 3 months so i am learning the in's and out's. any help would be great thanks.
32x11.50x15 BFG M/T's, Kenwood 769 CD player, MTX ThunderForms, Rockford Fosgate 400w Amp, Home Brew K&N Cold Air Intake, MagnaFlow Catback w/ 3 in tip and Vent Shades! Many more to come!!
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