Hi everybody!
I just bought my dakota 1 week ago and noticed a bad MPG, I drive it let's say 70% city and 30% highway and i get 12.5 MPG.
I also noticed a loss of power, lets say im driving on the highway and if i get my foot off the accelerator pedal, the idle speed goes down pretty quickly, and when i want to accelerate again, it needs a lot of power.
Also noticed some gas smell when engine is cold.
The truck has a REAL loss of power when im in rear. i have to press the pedal a lot before it moves!
I looked at a lot of threads but couldn't really find what i was looking for, my air filter is good, and oil is good too. I tried the seafoam, and also recently put a injector cleaner in my tank. And i went from 11.5 to 12.5 MPG.
I just bought replacedthe 2 upstream O2 sensors, and since then i have more power but MPG is still the same..
Should I replace the two post cat?

The truck is a 07 Dakota V6 3.7L 4X4 with 117k miles.

Thanks in advance for your answers, as i am pretty broke any help would be greatly appreciated ahah

 

definitely change out the plugs, they may be incorrect gap. try running some good gas into it, 93 and rip the snot out of it, carbon is a gas killer. check tire pressure, I usually run 40 psi on all 4

 

You talk about the spark plugs? Do you think that could cause bad MPG?
I put some good gas already thats the first things I thought about...
Same for the tires
Thanks!

 

yes, look at the plugs, made a difference for me in MPG.

and how did you do the seafoam? was it with the aerosol through the throttle body, or the liquid through a vacuum hose? i ask because if you used the liquid through a vacuum hose and use the wrong hose, then it might clean all cylinders.

I did the aerosol through the TB on mine, and it brought power, MPG and throttle response back to better then it was when it was new (or new to me as it was a year old when i got it). i did it once a year since then, and continue with my current vehicle. I added it to my yearly maintenance routine that i do.

 

I think the spark plugs are a good ideam, sorry I don't know much about mechanic, how many sparks plugs are in there? 6? I found a video that shows how to change them but he only changes two of them...
What kind should I buy?
I did the seafoam in spray on the throttle body, I probably gained 1mpg since then but still my mpg now is at 12...
Thanks again!

 

the 3.7 has 6 plugs (one per cylinder). the 4.7 has 16 (2 per cylinder). go with a copper plug, iridium or platinum plugs don't work very well in the engine. and don't do anything like an e3 plug. it works great at first but the e3 actually end up using more fuel.

 

Okey I saw where they are located I am going to do it today, I just ask for copper spark plugs at autozone? Also do you have any advices? like do I have to unplug the battery?
Thanks!

 

yes, undo one of the battery cables. do one plug at a time. This ensures that you don't put hte wrong wire on the wrong coil and cause more issues. the drivers side is easy, they are in the open. just undo the one connector on the coil, remove the bolt on the coil. twist as you pull up on the coil to remove it. then using a spark plug socket on a ratchet (with an extension to reach down that far) remove the spark plug.

The spark plug socket has a special rubber liner that holds onto the boot of the sparkplug making it easier to pull it out and put the new ones in.

the passenger side will require you to remove the intake tube going into the throttle body and loosen the air conditioning hose support bracket to gain access to the plugs on that side. just take your time. the second time i did mine it only took 30 minutes for me to do all 6. the first time took about an hour.

when reinserting, start screwing it in by hand before using a ratchet. that makes sure you don't cross thread them when they go back in.


as for what plug, the NGK v power copper (part number 6987) or autolite copper (part number 5224) should be good options. These are the ones that i can find online at autozone that will work for you.

good luck

 

Okey thanks for all those infos! I did it today and it was easier than what I thought EXCEPT, that one of the special rubber got stuck on top of one of the plugs but i finally managed to take it off.
I let it sit for 5 min, then drove it 5 min, and I supposed I will see if the mpg gets better in several days or weeks! I will let you know, but thank you so much to help people in this forum.

 

Okey, so I replaced the spark plugs, changed the oil, replace the oil filter, put an injector cleaner and high quality fuel and inflate the tires. No change in my gas mileage... Any other ideas? Maybe the pre cat O2 sensors? I am desperate....