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Bad MPG's

3K views 26 replies 19 participants last post by  firemn10 
#1 ·
I have been getting no more then 10 mpg for a while now and I am running out of money to full her up. And I hardly ever rev past 3000 rpm. Anyone know why it is so bad? I have a 02 1500 4.7, all fluids were changed and new spark plugs put in about 2000 miles ago. proformence mods. are a cold air intake, magna flow high flow cat and muffler dumped at bed. And 32 in tires which shouldnt make that much of a difference. Thanks
 
#2 ·
Hows the alignment, truck like to wander= sure sign of a needed alignment.
A brake caliper dragging ( a pull to left or right while brakingor just releasing brake pressure)
 
#4 ·
Winter blend fuel probably contributes to the problem. But there must be something else to. Check tire pressure. Do you need to replace your air filter? This might be some smaller problems all contributing to your lower gas mleage. What was your mileage before?
 
#5 ·
Yea something is def not right here. Especially without a lift and bigger tires. Just doesnt seem right, Get it checked out at a dodge dealership if there is one in your area.
 
#6 ·
Winter gas will drop your MPG's.
 
#7 ·
Try reseting the PCM's adaptive memory and see if it jumps up. With a cold engine, pull the PCM fuse in the fuse box, turn the key to "start" and hold for about 30 seconds (or until you hear a chime), take the key out, reinsert the fuse. Then start it up and let it idle for about 5-10 minutes, followed by some eggshell driving around the neighborhood with pauses to let it idle about 30 seconds at stop signs. Do that about 10-15 minutes and then go home and turn it off. Let the engine cool down and you should be good to go.

See if that helps. Sometimes when the seasons change and the weather changes dramatically the engine takes too long to learn the new conditions and MPGs suffer.

After that I'd clean the throttle body with brake cleaner, change the PCV valve, clean your EGR valve (brake or carb cleaner), and then start checking out the brake/suspension for possible drag. I assume you've changed the plug wires at least once since owning it. They can wear out too. After you do any or all of those, it's a good idea to reset the pcm again so the computer can relearn everything from scratch with the new stuff.

The 4.7 shouldn't be getting 10 mpg unless you just floor it all the time. I can however say that when I was getting my best mpg in my old '02 4.7 I was trying to keep my rpms below (or right at) 2k all the way up to shifts. I sometimes went up to 2.1 or 2.2k rpms to get it to shift over, but I coasted a lot and was turning in 16-17 mpg doing that. That only lasted a couple tanks of gas as it's no fun driving like that.
 
#8 ·
There is no draging anywere, i reset the pcm every once and a while and air filter is good. i didnt replace the wires or anying else but the plugs. What should I replace first? Thanks for all the quick replys.
 
#10 ·
I'd change the pcv valve, clean the EGR valve, and throttle body first and at the same time. That shouldn't be more than $30-40 buying the PCV and some spray brake cleaner. Those are just regular maintenance sort of stuff that probably haven't been done in awhile (easy to forget about). The PCV is easiest to reach with the intake taken off, and if the intake is off, the EGR and throttle body are just a few bolts and unhooking a couple of sensors. If you wanted to do it all in one shot, you'd be staring at the plug wires with the hemi hat off. Do them one at a time so you don't mix up the order.

Another one you might throw in the mix is a seafoam treatment if you haven't done it. I think it's like 1/3 in the tank, 1/3 in the crank, and 1/3 down the vacuum hose between the block and the brake booster. If you do put some in the crankcase, you'll need to change your oil within a hundred miles or so. Cleaning out the inside of the motor could free up some performance.

It would probably also be a good time to check out all your pulleys and your belt. A failing pulley could cause a little more parasitic drag on the motor. I don't know if it's enough to account for 10 mpg average though.
 
#9 ·
Forgot to say shes got 124 k miles on her.
 
#11 ·
My 02 4.7 Quad Cab only gets 10mpg.

I do have a remote start to let it warm up a little in the morning and my work is only 2 miles away so its just fully warmed up by the time I'm getting to work.

The last time I took it on a trip i did get 15/16 on the highway though.
 
#13 ·
Try resetting the PCM. What plugs did you use? If you used some fancy plugs or Platinum you'll hurt performance. Also try throwing on your factory intake. I've known three people now that have gone from aftermarket and had to run stock for a snorkel or another set up and found that MPG went up 3-4MPG!

Hand calculated here I'm at 24MPG :) My truck says I am getting 22MPG.
 
#14 ·
Replaced the pcv and cleaned the tb today I did not clean the egr valve tho. Going to drive around tonigh and see if it goes up. And the plugs i think were autolite.
 
#15 ·
I have read where the 4.7l is a really bad engine to NOT keep the oil changed in...this will result in gumming up of internals and could hurt the overall performance of the engine.

Look at AUTO RX...... This stuff really works! Not some majic potion that will change anything over night..but will clean the internals of your engine and re-condition your seals. This stuff worked great in my 98 Civic with a Rear Main Seal leak and valve train noise. Also look into the SeaFoam Treatment for your fuel system....You could try it in the crankcase but I do not like the idea of quickly letting all that gunk loose at once... I like the was the Auto RX works over 2500 miles "SLOWLY" Cleaning deposits....

The PCV and EGR need to be changed for sure!

*** What type of terrain do you live in? Hills / Mountains / Flat ??????

Check your Transmission Fluid or OIL ( Auto or Man ).... This could be hurting you.

Also check your rear differential fluid...

** Also check and make sure that you are not in 4-Wheel HI :cool:

Good Luck!
 
#17 ·
o2s are new and same with all the fluilds. some hills but mostly flat roads. Were exactely is the egr valve and I did just replace the pcv valve. And Ill take a look at auto rx and sea foam.
 
#19 ·
Yes... see the 4.7l is really working to get all that mass moving when unloaded and with stock wheels and tires....

Heavy wheels and larger tires not only take more power to get moving....they also lower ( Numerically --- 3.92 to say 3.55 gear ratio ) your final gear ratio causing more work to be done to accomplish the same task!

This along with a tune up would cause some drastic fuel mileage issues. Every 50 pounds you add to your truck will cause a % loss to your mileage....so clean her out, wash her off, and tune her up.....
 
#20 ·
I thought the 02 - 04 4.7s didn't have egr valves. That was something they added to the 4.7 in 05.
 
#21 ·
Did you have mileage problems before your tune-up? If not I suspect a bad plug or something got knocked loose during the process.
 
#23 ·
No..... It's just a fact of HP-TQ Compared to weight!

** I have owned a Dakota with the 4.7L ..... Durango with it..... and my Twin Brother had a 2004 2wd RAM, and now owns a 2006 4.7L, 4X4, LB with it.... Great motors no doubt.... They just have to work a little harder to do the same amount of work when all of your running gear is the same compared to a larger engine. The Dakota was a pulling BEAST with that motor! I put 80,000 HARD miles towing a RANGER Bass Boat all around the East Coast with it and never had one engine or tranny issue at all! The brakes were crap...but aftermarket fixed that!

SO.... No Bashing on the 4.7L mill....... Power to weight ratio is just it!
 
#24 ·
I do not know about the 2002's but on my 03 the o2's sensor wires are nickel or alluminum upto the connector, then its all copper the rest of the way to the other connections. Sometimes mixing these metals in a connection can lead to extreme corrosion of the pins and both sides of the wires at the point where they meet. Something to look into. goodluck
 
#25 ·
are u going by the milage computer? was it recallibrated for the tire size?
 
#26 ·
i get 13.5 ish with all the stuff i have done
 
#27 ·
I cleaned my EGR and PCV valves today. Didn't seem too bad but I figured what the heck, truck has about 59,000mi on it so I figured it couldn't hurt. Maybe I'll pick up some better fuel mileage. Whole job only took about 30 min. Dont lose/forget to put the gaskets back on for the EGR valve!
 
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