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GB2000
GenIII
4/22/2004
21:34:23
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 Subject: Horrid Gas Mileage
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Message:
What all could make my gas mileage so terrible besides a heavy foot and a bad 02 sensor? My truck has been getting downright TERRIBLE gas mileage lately and I'm not positive why. I started noticing it after changing the tb, thermo, and plugs. I still need to check the gap on my plugs to make sure they're gapped right...could that do it? I've got around 300+ miles on the truck since I reset the pcm after that tune up and I've gone through over a tank of gas...probably near 1 1/2 - 1 3/4 tanks. Any ideas would be greatly appreciated...with gas prices the way they are this is murder on the wallet. Oh yeah... my dak has about 47,000 miles.
Josh
Red 98 RC V6 2wd Single in/dual out exhaust (soon to be switched to a flowmaster 40 single in/dual out), Edelbrock 10" round air cleaner w/ K&N air filter, Autolite AP3923s, 180*F Thermostat, Ported V6 throttle body ...and much more to come!
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another mark
Dodge Dakota
JOIN HERE
4/22/2004
22:13:44
| RE: Horrid Gas Mileage
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I'm going through exactly what you are. My mechanic friend suggested to me to check the fuel filter. Maybe someday I'll look into the tank and see what's going on. I have a scanner and my O2s are both performing just like they should. I also have the 48mm TB, the MSD6A with 3923s at .60 and burning just fine. Even an electric fan and I'm not getting better than 13.5 mpg mixed driving.
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J and J Auto
GenII
4/22/2004
22:31:26
| RE: Horrid Gas Mileage
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Message:
Bad mileage
your sure o2 is ok ?
pletium gasket leak
Bad injector
injector sync.
put motor on TDC comp rotor aimed at or near #1
plug wire, there is a line on pickup plate the
edge of the rotor should be just behind the line
when looking from front of truck +3 look straight
down over top of dist, 1/2 bolt to move and a
pain to get to
180 thermo running cold, I have seen many that do
stant superstat, robertshaw are good ones
Bad IAT reading cold, if you relocated move back
to intake not all trucks react well to this mod
engine temp sensor reading low, both of these will
make you run rich and hit gas mileage
check these things first
Larry
J&J Auto
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daffydak
GenIII
4/22/2004
23:46:09
| RE: Horrid Gas Mileage
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Message:
Welcome to my world josh LOL. I get crappy mileage, but at least i have fun doing it!! I think most of my problem, is the 180* t stat. its an AutoZone failsafe. It might be running a lil cold (it almost touches the #2 (the 2 of 210 no where near the actual 210 mark) on the temp gauge about 1/3 of the way up) I wish i had a more accurate gauge, but I’m not losing any sleep over it. maybe this summer i will put a jet or stant 180 in and double up the thermostat housing gasket (leaks just enough to leave whitish marks around it) and I haven’t lost any coolant since last summer!! I am thinking about my 02 sensor too my truck has almost 53k on it and I think the 60k mark is o2 sensor time.
Sorry for the long winded post.
Dan
mopar=mopower
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GB2000
GenIII
4/22/2004
23:55:43
| RE: Horrid Gas Mileage
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Message:
I'm hoping that my problem isn't the thermostat...that thing was a biznatch to change! Mine is a Stant Superstat from Advance Auto Parts.
Josh
Red 98 RC V6 2wd Single in/dual out exhaust (soon to be switched to a flowmaster 40 single in/dual out), Edelbrock 10" round air cleaner w/ K&N air filter, Autolite AP3923s, 180*F Thermostat, Ported V6 throttle body ...and much more to come!
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Wadak
Dodge Dakota
JOIN HERE
4/23/2004
00:11:58
| RE: Horrid Gas Mileage
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Message:
Larry if you suspect a bad iat could be affecting their mileage by reading too cold the could go to Radio Shack and get a couple of resistors. Install them one at time and see if mileage improves. I checked my 97 factory service manual. The chart indicates IAT sensor resistance reading for 77 degrees between 9000 and 10000 ohms. 86 degrees 7000 to 8000 ohms. 104 degrees 5000 to 6000 ohms. They could disconnect the connector from the IAT sensor place one lead of each end of the resistor into the connector, then cover over with electrical tape to prevent the connection from shorting out and leave it ths way for awhile. Then fill up with gas and check their mileage, if it improves replace the IAT. I bought a pack of resistors from Radio Shack and palcyed around with different values to see where my truck would run best. I found that right around 30000 ohms worked best for me at the time outside temperature was between 30 and 40 degrees. I ended relocating my IAT from intake manifold to the AIR tube and it has been working good for me. I constantly monitor ouside air temperature vs air intake temperature with the cheap digital temp gauges with the 10 ft cord and the sensor on the end.
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another mark
Dodge Dakota
JOIN HERE
4/23/2004
00:13:37
| RE: Horrid Gas Mileage
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Message:
Hey Daffy, I understand the need to want to replace things that are old, but as long as you have a scanner and can read the O2 and it's flip flopping between that .0 to .9 range I don't think that an O2 would need replacing just because it's been in for a few years. I just hate to see someone spend money that doesn't need spending. I've seen a couple posts talking about mileage and how the O2 should be replaced at such and such a time, I just don't agree with it...yet. I've got a 99 with 75,000 and my O2s are still working fine. Must be another one of those damn sensors.
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?
Dodge Dakota
JOIN HERE
4/23/2004
08:53:24
| RE: Horrid Gas Mileage
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Message:
Re O2 , my 95 has just over 100,000 miles
still original sensor .
Like " another mark " , I don't think
that should be causing your problems !
But injectors getting ' dirty ' ?
Have you fellas used any inj. clean lately ?
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Bob Lincoln
Dodge Dakota
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4/23/2004
09:05:41
| RE: Horrid Gas Mileage
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Message:
Check fault codes. If the O2 sensor were bad, it would still be under federal warranty.
The change from 195 to 180 thermostat does make more power, but does hurt gas mileage noticeably. What was your mpg before the work?
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daffydak
GenIII
4/23/2004
09:58:54
| RE: Horrid Gas Mileage
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Message:
thanks everyone (not trying to steal your post josh)
I run injector cleaner about 2 times a month and run premium fuel(turbo blue last week, WOW!!) I'm going to check my 02 with my volt meter. it has to be warmed up to make a reading, correct?
wadak, thats a good idea. I think I will try that. I dont have a scanner, my truck runs great otherwise (except under normal accel it only stays in 3rd for 1-2 seconds, then it bogs in fourth until i get to 45 then the tq converter locks) could that be my tps? its fine if i'm on the gas pretty good just under normal accelleration...
my tv cable is adjusted properly (and if i recall correctly that only controls 1st and 2nd) I have a modded one (tps) ready to install, I just was bit by the lazy bug and havent gotten around to it yet...
i dont remember my mpg before the 180* stat. i also have a "useless" jet stage 2 chip, could that kill mileage too?
thanks again
Dan
mopar=mopower
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Bob Lincoln
Dodge Dakota
JOIN HERE
4/23/2004
10:12:51
| RE: Horrid Gas Mileage
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Message:
You don't need a scanner to check fault codes, just use the key method:
http://allpar.com/fix/80s-codes.html
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daffydak
GenIII
4/23/2004
10:26:41
| RE: Horrid Gas Mileage
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Message:
thanks bob. i dont think that will work on my 98, but I will give it a shot!
allpar is such a great site, all the info you would ever want on mpoar engines!
Dan
mopar=mopower
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daffydak
GenIII
4/23/2004
10:32:02
|  RE: Horrid Gas Mileage
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Message:
nope it didnt work. I even tried holding the trip/reset button to no avail.. it sure gave my fuel pump a workout though :-) the check engine light just came on once for about 2 seconds just like a normal startup....
Dan
mopar=mopower
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99DAK
Dodge Dakota
JOIN HERE
4/23/2004
10:54:20
| RE: Horrid Gas Mileage
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Message:
Doesn't work on a '99 either. If you hold the odometer reset while turning the key on it'll do the gauge/inst.panel diagnostics, but that's it.
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JoesDak
Dodge Dakota
JOIN HERE
4/24/2004
00:07:54
| RE: Horrid Gas Mileage
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Im having a problem with bad gas milage too.But not city driving.Just out on the highway is when it uses the gas.I can get about 200miles a tank in the city.But if i take it out on the highway i only do about 60-70miles a tank.And thats running about 70mph.Anyone know why this would happen?I dont do much driving on the highway but when i do i get really bad gas milage.
Any help here would be really great.
Thanks
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another mark
Dodge Dakota
JOIN HERE
4/24/2004
01:17:34
| RE: Horrid Gas Mileage
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Message:
I just installed a new set of fuel injectors so it's not that. My best ever mileage when the truck was new in 99 was 15.7 now it's 13.5.
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maby
Dodge Dakota
JOIN HERE
4/24/2004
07:56:49
| RE: Horrid Gas Mileage
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Message:
it could be the 180 stat.
i have a 98 rc v6 auto and get 22mpg.
my mods are,bed cover,dual out catback system,k&n drop in,bosh plat-4 plugs,brass cap&rotor,electric fan,40 psi in tires,synth oil,
i lost 2 mpg with a 180-stat-went back to 195
next ill try the timing advance mod.
also did you port the TB ?
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daffydak
GenIII
4/24/2004
14:04:23
|  RE: Horrid Gas Mileage
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Message:
my v8 tb could attribute to a mpg loss, more air needs more fuel... oh well you want to play, you gotta pay!!
Dan
mopar=mopower
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GB2000
GenIII
4/24/2004
15:39:23
| RE: Horrid Gas Mileage
IP: Logged
Message:
I pulled a plug and checked it...not tan, it's got a lot of carbon built up around the bottom and the threads like it's probably running rich. The ceramic-like part by the electrode is still white like the plugs were when brand new...gap too wide or too small?
Josh
Red 98 RC V6 2wd Single in/dual out exhaust (soon to be switched to a flowmaster 40 single in/dual out), Edelbrock 10" round air cleaner w/ K&N air filter, Autolite AP3923s, 180*F Thermostat, Ported V6 throttle body ...and much more to come!
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Bob Lincoln
Dodge Dakota
JOIN HERE
4/24/2004
15:52:57
| RE: Horrid Gas Mileage
IP: Logged
Message:
Probably too wide - set to .035" on new plugs.
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d_nuckolls
Dodge Dakota
JOIN HERE
4/24/2004
21:58:22
|  RE: Horrid Gas Mileage
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Message:
I have a 98 rc and am also getting bad mpg about 15-16 on a 30 mile commute to work. what would be the best mods to enhance mpg? thinking about new injectors any suggestions on what to get(oem or other)? Thanks.
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