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MWilli50
Dodge Dakota
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1/27/2010
12:39:12
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 Subject: 2003 Dakota gas mileage issues
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I'm at the end of my rope here. Let me explain.
I have a 2003 Dodge Dakota SXT. It's an automatic V6 with around 79000 miles on it. I've taken care of it, performed tune-ups, etc. However, around a year ago the gas mileage started falling and the check engine light came on. Originally, a tank could last me 280-300 miles. Now, I am lucky to break 200 and average around 11 miles to a gallon. The engine codes are always the same: large emissions and small emissions leak. I took it to two different mechanics who failed to diagnose the gas mileage issue or correct the emission issues before I took it to a local Dodge dealership. They say that they have no idea what could be causing my gas mileage issues, nor have they ever seen a Dakota do that. They claim to have fixed the issues surrounding the engine light, but that those codes are not impacting the mileage.
Anyone have any suggestions? I really don't know what else to try.
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hmmmm
Dodge Dakota
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1/27/2010
12:49:35
|  RE: 2003 Dakota gas mileage issues
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Slow/Lazy O2 sensor/sensors
Does the motor ping when under load?
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Mwilli50
Dodge Dakota
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1/27/2010
14:58:13
| RE: 2003 Dakota gas mileage issues
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Let me correct myself. The truck has 71000 miles, not 79000. Not a big difference, but still worth mentioning.
I don't believe so. Mechanics have always commented on how the truck idles and runs fine. The only noise I can think of that the truck makes is a slight whirring noise while accelerating or at higher rates of speed. But, the dodge mechanics told me it was nothing. That is a pretty recent development, too.
Just picked the truck up from the dealership. Engine light is off, but it has come back on 80 miles after having the vacuum hoses fixed before.
I will admit that most of my driving is in the city, but it still should not be getting this bad of mileage. I use regular gasoline, occasionally use fuel treatment or injector cleaner, and change my oil/perform tune-ups regularly.
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fotodak
Dodge Dakota
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1/27/2010
22:46:45
| RE: 2003 Dakota gas mileage issues
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+1 on lazy O2 sensors, and add a clogged catcon.
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Mwilli50
Dodge Dakota
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1/28/2010
00:17:27
| RE: 2003 Dakota gas mileage issues
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Do you think it could be the 02s or catcon if no engine code is present?
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?
Dodge Dakota
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1/28/2010
08:48:20
| RE: 2003 Dakota gas mileage issues
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Yes on the 02 sensors - the one , or two in
front of the 'cat' .
They will not throw a code until totally gone
-- but - truck would be running real bad long before that .
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explained
Dodge Dakota
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1/28/2010
12:08:47
| RE: 2003 Dakota gas mileage issues
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A slow and/or Lazy O2:
Working and adjusting air fuel ratio so the pcm will not throw a code.
However slow/lazy to adjust ratio's results in poor fuel economy.
(had this very same problem with my truck)
NOTE:
This is not a positive but a very strong possibility.
There is a way to check and test the O2's
to see if they are slow/lazy.
Larry of J&J auto knows the whole procedure.
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MWilli50
Dodge Dakota
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1/28/2010
14:47:29
| RE: 2003 Dakota gas mileage issues
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Thank you for the replies. I am very appreciative of them.
I will research the 02's next. I suppose I could go ahead and replace them considering the truck's mileage. It will be time soon enough.
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me again
Dodge Dakota
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1/28/2010
15:33:19
| RE: 2003 Dakota gas mileage issues
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Larry also had done some testing and research with dif. O2 sensors. He found that NGK's NTK O2 sensors seemed to have worked best with the 3.9's.
He also found that NGK V-power plugs part# FR5 were the best plugs for these motors.
I'll start a new thread and see if we can get Larry's attention.
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03kota11
Dodge Dakota
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2/10/2010
19:39:59
|  RE: 2003 Dakota gas mileage issues
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Listen if it were to be an 02 problem, the pcm would autimatically throw a code telliong that they were weak or even bad. My truck has had the same code come on for around 3 months now.....yes the problem is causing a loss in gas mileage as it is for me. The is a vacuum canister located on the engine that tends to clog or even leak alot. the canister is fairly noticeable. I havent looked into it yet, but have had good advice from some pretty good gearheads. try this and cherck your mileage. when i get a chance, i will too
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daddio
Dodge Dakota
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2/10/2010
20:19:51
| RE: 2003 Dakota gas mileage issues
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Are you still getting the leak codes? If you get the large leak code, check the hoses to the charcoal canister first. It's located under the cab in front of the fuel tank. There are prone to cracking and leaking. You can replace them with some rubber fuel line of the same size.
Small leak usually indicates a bad fuel cap. Change it. After you take care of those check your fuel mileage again.
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Mwilli50
Dodge Dakota
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2/10/2010
20:29:23
| RE: 2003 Dakota gas mileage issues
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Alright, so here is where my truck stands so far:
The check engine light has been off for roughly 150 miles. So, I would surmise that problem (the evap leaks) is fixed. But, I haven't driven it enough to really tell if my gas mileage is improving.
I have changed the gas cap before and it led to no change with the check engine light, so that was not it.
I'll look into the charcoal canister. Also, I will keep you all informed as to the gas mileage I get over the next few days.
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daddio
Dodge Dakota
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2/11/2010
20:23:02
| RE: 2003 Dakota gas mileage issues
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Try running a couple of tanks of fuel to check the mileage and let us know what you find.
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Mbornstein
Dodge Dakota
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2/20/2013
12:23:54
| RE: 2003 Dakota gas mileage issues
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I suggest replacing oxigen sensors, fuel injectors, and a new catalytic converter.
Also 71,000 miles you probably need a new intake manifold gasket, intake manifold gakets need to be retightened a week after you install them with the engine still warm. Replace vacuum hoses if they are dry or brittle. Replace vacuum contol module bolted to the top of the intake manifold. Also change transmission oil and filter.
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