really bad fuel mileage 10MPG

[ramguy1500]

hey guys i need some help on figuring out why my o4 ram 1500 5.7 hemi is burning so much fuel. im getting 10mpg and cant figure out why.

ive owned this truck for 1 year now and im the second owner. ive replaced the spark plugs when i got the truck as well as the 02s. i have a bad cat bank 2 sensor 2 is telling me the cat is below efficy threshold and i don't know if that is the source of my problem or not. my iat and map sensors are fine. fuel pressure is good. cleaned throttle body. i do how ever have slit rough idle but no engine codes or miss firing. i also dont let the truck sit and idle long and dont stomp on it after stops.

 

[srv1]

im getting 10-11 in my 04 but i figure its because the truck is 17 yrs. old and i also drive like a f*****n cowboy.

 

[srv1]

was your mpg better when you got the truck?

 

[MoPowered]

Are you getting any miss when you place the engine under load ? You can do it simply by power braking it and see if the misfire get’s worse. Your truck is an 04 and I would gather a bunch of miles so it would be hard to say what could be causing it. You’ve already started at so e points by plugs, IAC and throttle body what about MAF ? Air cleaner and coil packs. And if your Catalytic Converter is clogged it will cause fuel ratings to suffer.

 

[ramguy1500]

Are you getting any miss when you place the engine under load ? You can do it simply by power braking it and see if the misfire get’s worse. Your truck is an 04 and I would gather a bunch of miles so it would be hard to say what could be causing it. You’ve already started at so e points by plugs, IAC and throttle body what about MAF ? Air cleaner and coil packs. And if your Catalytic Converter is clogged it will cause fuel ratings to suffer.

i will give it a try and see what happens, i thought the 04s didn't have mafs but ill check again. brand new air filter last oil change and i also replaced the intake manifold gaskets because i cleaned it out due to the amount of oil sludge inside of it.

when i changed out the o2 when i got the truck i noticed that bank 2 had heavy carbon deposits over the up stream o2 and the down stream but not bank one. i have no other check engines codes either. the coil packs and wires are oem and haven't been replaced from what i can tell. i alo used ngk iridium plugs

 

[Cableman]

My 08 with under 100k was only getting 10-11 around town, my 16 is at 13 with this winter gas otherwise its around 15 local.

 

[LoneWolf3574]

i will give it a try and see what happens, i thought the 04s didn't have mafs but ill check again. brand new air filter last oil change and i also replaced the intake manifold gaskets because i cleaned it out due to the amount of oil sludge inside of it.

when i changed out the o2 when i got the truck i noticed that bank 2 had heavy carbon deposits over the up stream o2 and the down stream but not bank one. i have no other check engines codes either. the coil packs and wires are oem and haven't been replaced from what i can tell. i alo used ngk iridium plugs

You have a MAP sensor at the front of the intake manifold, basically centerline. With the Iridium plugs, you are wasting your money, the Hemi notoriously hates just about anything but copper plugs. If you are going with NGK, my preferred brand btw, go with NGK 5306 LZTR4A-11 otherwise stick with the OEM Champion RE14MCC4 or Mopar SPRE14MCC4.

 

[MoPowered]

i will give it a try and see what happens, i thought the 04s didn't have mafs but ill check again. brand new air filter last oil change and i also replaced the intake manifold gaskets because i cleaned it out due to the amount of oil sludge inside of it.

when i changed out the o2 when i got the truck i noticed that bank 2 had heavy carbon deposits over the up stream o2 and the down stream but not bank one. i have no other check engines codes either. the coil packs and wires are oem and haven't been replaced from what i can tell. i alo used ngk iridium plugs

I should of said Air Charge Temperature Sensor commonly know as a MAF sensor. If it’s bad it changes air/fuel mixture ratio’s and will affect mileage. Not the MAP Sensor which is Manifold Absolute Pressure 2 different thing’s. True on the plugs, Hemi’s like Copper you can also index the gap toward the intake port’s. You can also opt for a slightly cooler plug and run a larger gap. Change out those coils and did you buy OEM 02 sensor’s ? Yet again they hate any generic 02 sensors.

 

[ramguy1500]

I should of said Air Charge Temperature Sensor commonly know as a MAF sensor. If it’s bad it changes air/fuel mixture ratio’s and will affect mileage. Not the MAP Sensor which is Manifold Absolute Pressure 2 different thing’s. True on the plugs, Hemi’s like Copper you can also index the gap toward the intake port’s. You can also opt for a slightly cooler plug and run a larger gap. Change out those coils and did you buy OEM 02 sensor’s ? Yet again they hate any generic 02 sensors.

I will changing the plugs out this week. The map sensor is fine. I've got oem O2 sensors in it and what would recommend the spark gap to be?

 

[MoPowered]

If your running stock plugs run stock gap, if you go a range cooler open the gap. On my 12 it calls for 0.044. With NGK’s Iridium 4469 which come pre-gapped but check to be sure. There are allowable gap differences but remember gaps open with mileage with electrode wear that’s why we’re replace them. If you run them up higher it could cause some hesitation and some pre fire before piston stroke cycle. If you run it smaller it will cause a weak spark and won’t run efficiently. These are all old tricks from our carb and choke days in trying to get the most bang for your buck. Today’s engines take care of that today especially with the hemi dual plug. But you can still index them toward the intake ports and try a slightly larger gap to the top allowable index range.

 

[ramguy1500]

Ok will give it a try and update here. I also don't have the dual plugs. I only have 8 in my hemi

 

[MoPowered]

Ok will give it a try and update here. I also don't have the dual plugs. I only have 8 in my hemi

Much cheaper for you, lol.

 

[Thundr]

Did you lift it or any mods with tires?
I have an 05 w/6inch lift 3 inch body and running 38's for tires and I get 10 on the highway. 14 mpg if I run 35's.
I updated my could packs to late model with BBK Headers a ram air hood direct flow and a couple of other odds and ends

 

[Snake15eyes1998]

...... I mean no disrespect. But your driving a 5.7 V8........V8. I average 11.5MPG. there should never be a MPG worry on a truck forum. Again, I mean no disrespect. Just being honest. Hope your MPG goes up man.

 

[3pedals]

Is it lifted or running bigger tires? All stop and go driving?

My truck (08 4.7 4wd 6spd) is tied with a Lincoln pickup for the worst rated fuel economy of any factory vehicle in 2008 (12 city 16 highway). I drive it like a total a$$hole, with lots of full throttle, some attempted drifting, and excessive heel/toe downshifting. Given all of this, I usually average around 12.5-13mpg combined on 87 octane, with my worst ever unloaded tank being about 10.5mpg. Worst I’ve ever seen was in the low 9’s, but that was with a maxed out payload on an especially angry day.

I guess my point is something is definitely off to get 10mpg in your truck, unless it’s all city driving and/or you’ve got bigger/heavier tires