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fastyz400
Dodge Dakota
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12/03/2003
10:44:28
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 Subject: RE: Help! Severe Mileage drop
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I put money on the O2 sensor. The computer does not pick up a falt code until it completley fails. If, you have sever carbon buildup on it this would cause it to send false info to the computer.
There is a resistance check with an ohm meter that you can do for the o2 sensor, but don't know if it will tell you that it has too much carbon buildup or not. This proceduce can be usually found in your Chilton books.
This is how i would go about handling his situation:
1. Take a look at your plugs, see if you are lean or rich. If, you are either, the O2 sensor is probably bad. There are 2 o2 sensors, one before the cat and one after. Take a look at bosch's website to see if they make a universal for your model. It's heck of a lot cheaper than your oem. Read my post on O2 sensor.
2. If, you see a lot of carbon deposits on your plugs, do a professional injector cleaning, found at Pep Boys for $79. Then Change out the O2. This is done so the new o2's will not see all the crap from the cleanng.
If, your cat was bad, it would serverly restrict air flow. Causing your car to die after 10-20 miles. This happened on my 91 Grand am.
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Mr.Sleepy
Dodge Dakota
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12/03/2003
14:29:48
| RE: Help! Severe Mileage drop
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To answer the first post...
I haven't been on a all highway trip yet, so I can't vouche for any 1 tank trip figures. I will look into that soon. My first mileage drop occurred after the addition of my exhaust. However it was installed for 3 months before the drop occurred. These drops occur rapidly. My first drop literally happened after a fillup which was 20 miles lower than usual, I blew it off thinking it was because I was hot rodding most of that week. The following fillup was at 50 miles less per tank and never recovered. It was definately not a slow process of decent, it was very sudden. This same condition happened just recently during the first month of cold weather we just had. Very sudden drop in mileage.
Fastyz,
I'll have to look into that. It's probably one of my last hopes of getting this situation fixed.
Thanks for your help and input guys, it has helped out quite a bit and I'm glad that you folks spent the time to lend your advice on this matter. If any of you might have some more to say on this matter or if you find out some news, please post it, I check this board at least 5 times a day. Thank you.
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VeryBigBear
Dodge Dakota
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12/03/2003
14:55:45
| RE: Help! Severe Mileage drop
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No expert here, but on my '97 CC 5.2 4x4, I get a professional injector service every year, add an occasional can of BG injector cleaner (on long highway trips), 3K mile oil changes like religion and added a K&N air filter, which I get serviced every 4-6 months.
At 142k miles, it gets better gas mileage now than when I bought it at 76K. I keep thinking of getting rid of this truck for a newer one, but the damned engine is actually HAPPY these days.
But that's low hanging fruit, I have a much older and longer-driven truck. A newbie's guess here is a gummed up cat or failing O2 sensor.
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BadMoFo
Dodge Dakota
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12/03/2003
17:15:17
| RE: Help! Severe Mileage drop
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Been drag racing any Hemi Durango's you moron?
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Mr.Sleepy
Dodge Dakota
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12/04/2003
13:17:01
| RE: Help! Severe Mileage drop
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Bad Mofo, Isn't Net Nanny supposed to keep little idiots like you off of adult boards?
Anyway... Tried some fuel system cleaner, and I am going to purchase those bosch O2 sensors. See if this helps out any.
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Wolverine
Dodge Dakota
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12/04/2003
14:17:16
| RE: Help! Severe Mileage drop
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(Another) amature's opinion:
My brother asked me if my truck got louder over time after putting on a Flowmaster 2 chamber. He says the better flowing muffler might "clean out" the cat, thus making it louder. Maybe some "cleaned out" junk fouled your sensor(s). Maybe the increasingly better flow demands more fuel and will naturally drop mileage (but increase power).
Personally, I just added the Flowie and K&N somewhat recently and experienced a 2 mpg Jump at the first calc. I'll keep you posted as to any adverse affects like what you've been seeing. Also, I don't remember what year your truck is, or if that even makes a difference. I've heard there was a significant jump in quality between '00 and '01. Fortunately, this was after I got my '01 Quad Cab 4x4. I'm now getting about 15 mpg, and started not draining the tank between fill ups (I heard running the fuel low makes the fuel pump work harder and will make it die sooner).
Enough rambling. Hopefully this helps.
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fastyz400
Dodge Dakota
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12/04/2003
15:19:39
| RE: Help! Severe Mileage drop
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Mr. Sleepy,
You gonna get the bosch universal o2 sensors?
Checked with dodge today, the o2 sensor from dodge is a chrysler o2 sensor, so, i would go with the bosch.
Again, you should try to take a look at all the plugs first.
If, only one or two of the plugs show a rich condition that means, it could be either your plugs or the spark plug wire going to the plug. Go to the link below to take a look at the different conditions of your spark plug.
http://www.autolite.com/tech/PlugTips.pdf
A bad o2 sensor would show all 8 about the same condition.
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pkdak
Dodge Dakota
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12/04/2003
22:10:34
| RE: Help! Severe Mileage drop
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Mr. Sleepy
Computer reflash around here is about $80.00. you might check with your dealer. You should also have your dealer check for TSB's for your truck and computer. I got my first reflash for free because it is an emissions control device and they cover these for longer than standard 3/36. They do not advertise out loud about some items having longer coverage than 3/36. I would ask them about my 02 sensor because it also is an emissions control device and you might get some diagnostics for free. Let me know if you get any or no results. PKDAK
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Mr.Sleepy
Dodge Dakota
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12/05/2003
08:23:54
| RE: Help! Severe Mileage drop
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Do you think they will give me flak about having a aftermarket exhaust on my truck if I take it in to have the O2's diagnosed? I had them complain about it before for a completely different reason.
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fastyz400
Dodge Dakota
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12/05/2003
11:10:36
| RE: Help! Severe Mileage drop
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yes,
The dealer will most likely complain about it. They will probably try to tell you that is your problem, another way of saying, they have no clue. lol
It shouldn't make a difference. The muffler is after both the cat and o2 sensors.
Just curious, what water temperature does your truck run at? Is it running at normal temp?
Mr. Sleepy, you really need to look at your plugs. They will tell you a lot. It's an easy thing to do. Then compare your plug to the plug condition at the autolite website. This will give you and me an better idea about what's going on with your truck before you take it in and have the dealer screw you when your not looking.
http://www.autolite.com/tech/PlugTips.pdf
You need the pdf reader from adobe, it's a free download.
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fastyz400
Dodge Dakota
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12/05/2003
11:21:08
| RE: Help! Severe Mileage drop
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Oh,
If you take it to the dealer, they will install the same crapy o2 sensor again. Get the bosch.
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fastyz400
Dodge Dakota
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12/05/2003
11:34:55
| RE: Help! Severe Mileage drop
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Take for example:
Plug 1: Normal
Plug 2: Rich
Plug 3: Rich
Plug 4: Lean
Plug 5: Lean
Plug 6: Normal
Plug 7: Normal
Plug 8: Normal
Plugs 2 & 3: could be the wire or plug that are bad, because, it's showing a rich condition
Plugs 4 & 5: It could be a pluged injector. Because, all the rest are normal or rich
Plug 1: Rich or lean
Plug 2: Rich or lean
Plug 3: Rich or lean
Plug 4: Rich or lean
Plug 5: Rich or lean
Plug 6: Rich or lean
Plug 7: Rich or lean
Plug 8: Rich or lean
Most likely in this condition it would be your o2 sensor, because, all of them are uniform.
If you notice your truck serging it could be the throtle position sensor or o2 sensor.
By taking it to the dealer, they will charge you $80 for the just look at it, then they will charge you labor and install. Woo, that will be like $350 when your done.
If you did it yourself, That would be like replacing all the possible part and still have money to spare.
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pkdak
Dodge Dakota
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12/05/2003
22:54:20
| RE: Help! Severe Mileage drop
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Mr. Sleepy
When you take your truck to the dealer inform them that the sensor does the same job no matter what round hunk of metal it's in. Did you know that it is illegal for a dealer to give you flack about after market equipment on your truck.I.E. warranty for covered items on your truck. CHECK IT OUT. I had my computer reflashed after installing an fipk on my truck. The dealer tried to say that warranty would not cover my reflash, but there was a TSB for my truck to reflash the pcm and I told them that the fipk would change the computer itself. SO they did it. (AT NO COST TO ME). The second reflash was when I installed new larger wheels and tires. This made a BIG difference in mileage, shift points and highway RPM's. Let me know if you have any other questions
PKDAK
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therealanswer
Dodge Dakota
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12/06/2003
17:22:14
| RE: Help! Severe Mileage drop
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every winter the fuel refiner in your area re-formulates the gas you purchase in the colder months of the year to make it easier to start your car/truck in the winter. An unfortunate side effect to this re-formulation is a fuel that does not give as good as milage as you got in the warmer summer months. Sorry but no amount of changing computers or O2 sensors or other engine senors or components is ever going to change this. It is a fact of life and you just have to live with it or move to a warmer winter climate. All these other guys that gave answers contrary to this are sadly mis-informed, my brother-inlaw's sister-in-law is the head chemist at Sunoco's Toledo Refinery and has verified this, so I have it from someone that actually changes the formula that you burn in the winter.
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Kowalski
Dodge Dakota
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12/06/2003
17:45:10
| RE: Help! Severe Mileage drop
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Maybe, but it seems like he might be complaining about a bigger loss than this would explain. I still get around 15 mpg with my 2K 4x4 4.7 with the reformulated gas. Did you check for a clogged cat ? Check your manifold vacuum, probably between 17 and 22 inches at idle. It should be 3-5 inches higher at 2500-3000 rpm; if same or lower you have a restricted exhaust. Or if its real bad it might glow cherry red !
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fastyz400
Dodge Dakota
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12/06/2003
23:31:05
| RE: Help! Severe Mileage drop
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I will have to agree with Kowalski, the consumtion that Mr. Sleepy has is much greater than the change in gas formulation.
Good answer Kowalski. That is another way to check for a restricted exhaust.
Just wondering Mr. Sleepy, are you pushing on the gas pedal further to maintain the same speed?
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Sesquash
Dodge Dakota
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12/07/2003
14:54:06
| RE: Help! Severe Mileage drop
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Try something as simple as this...for I think that the PCM is way too sensitive to changes in driving habit....and adjust too quickly...and not fast enough when a light throttle load becomes the norm, again...
Let the car sit and idle for an hour or so. Yep..just idle. I think that it causes the PCM to alter its fuel flow, whatever..for when I did just that the other day, my mileage went up a full 3.5 mpg.
I think all this electronic crap is just that...too much crap running the 'tune' of the engine....
Give me a two or four barrel any day...
Sesquash
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fastyz400
Dodge Dakota
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12/10/2003
10:29:47
| RE: Help! Severe Mileage drop
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Mr. Sleepy,
Did you ever get your problem fixed? I am curious to know what happened.
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Mr.Sleepy
Dodge Dakota
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12/10/2003
17:06:08
| RE: Help! Severe Mileage drop
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I've had a busy week so I haven't been able to tinker with the truck, but I have done a 90% highway trip and got 15 Mpg out of my truck on a average figure based on miles and gas pumped into the tank. I always top off the tank so this is reasonably accurate. This is about 30 miles more per tank, but I was also going around 60 mph on the freeway most of the time with NO hard acceleration. I will pull my plugs this weekend and inspect the O2's while i got my hands dirty. I just had a tune up done so I wanted to wait a tank or two prior to pulling them. I will keep you guys posted.
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fastyz400
Dodge Dakota
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12/10/2003
18:50:30
| RE: Help! Severe Mileage drop
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wooo,
15mpg @ 60mph. I have a 2000 durango 5.9. at 60 on the trip computer, it registers 18-21 mpg. Depending on incline.
hmmmm, need to check those plugs Mr. Sleepy
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