Very poor gas mileage!! Suggestions??

[oceanside78]

So a little less than a year ago I purchased a 98 T4R limited, V6 auto with ~145k miles. I bought it very well maintained but no service history. I've kept up on the maintenance, and absolutely do no drive it hard, nor does my wife. The driving is split 50/50 city/highway and my gas mileage has progressively gotten worse. It seems I average ~5 miles less per tank each fill up for the past couple months. I used to get around 220 a tank, which I thought was low but now I'm down to 185 this last tank, which is horrible IMO. I recently chAnged oil, filter, air filter, and cleaned the MAF. My only thought it fuel filter but I have no power loss, which was a main sign in my last vehicle when it went bad. Any suggestions? My wife is about to travel cross country and I sure would like to get the most out of my mileage, as we don't have money to purposely burn. HELP!!!

 

[brian2sun]

Are you sure it's your mpgs that are low or is it your fuel gauge? How many gallons are you putting back in when you fill it up? Are you lifted? Big tires?

 

[FdcCal]

I would replace the spark plugs with the correct NGK dual electrode type, the plug wires, and both O2 sensors. Now, if these have been done recently, there may be other problems. The plugs need to be replaced between 10 and 15000 miles, and the O2 sensors are tired by 100k, even if they don't cause a code. My .02, YMMV.

 

[rangermenace]

I would replace the spark plugs with the correct NGK dual electrode type, the plug wires, and both O2 sensors. Now, if these have been done recently, there may be other problems. The plugs need to be replaced between 10 and 15000 miles, and the O2 sensors are tired by 100k, even if they don't cause a code. My .02, YMMV.

mine has around 107k and never had the O2 sensors replaced, why would they need to be and what do they cost?

 

[Orange Skullz]

So a little less than a year ago I purchased a 98 T4R limited, V6 auto with ~145k miles. I bought it very well maintained but no service history. I've kept up on the maintenance, and absolutely do no drive it hard, nor does my wife. The driving is split 50/50 city/highway and my gas mileage has progressively gotten worse. It seems I average ~5 miles less per tank each fill up for the past couple months. I used to get around 220 a tank, which I thought was low but now I'm down to 185 this last tank, which is horrible IMO. I recently chAnged oil, filter, air filter, and cleaned the MAF. My only thought it fuel filter but I have no power loss, which was a main sign in my last vehicle when it went bad. Any suggestions? My wife is about to travel cross country and I sure would like to get the most out of my mileage, as we don't have money to purposely burn. HELP!!!

A little more throttle here or there over the course of a tank of gas can make a big difference. Stop & go traffic, little more city driving, idling time at a drive thru, ect.

A better guage of mileage is checking it after a half tank of gas on a few occasions back-to-back or on an extended trip of some sort.

I have a '98 Limited also, best mileage I ever saw was right at 20 mpg on a single tank of fuel on a trip of 800 miles. During that same trip I got as low as 16...it may also vary on the brand/octane gas you run.

 

[oceanside78]

Brian, slightly bigger tires, highway terrains. About an inch over stock. Swapped to tundra rims. I believe they are 265 70 17s. But the mileage was like this before. I'm putting 14 gal in it everytime. Run it till the gas light just begins to turn on, and refill. 14.xx gal each time.

It probably needs plugs and wires, but I've never seen plugs and wire cause a 5 mpg loss. Maybe 1-3 at most.

The crappy part is I deploy this week so I don't have the time to do it myself so my wife has to take it in before she drives home

 

[brian2sun]

Plugs and wires could definitely help.

 

[oceanside78]

I'll give that a shot then. I might as well do a fuel filter as well, don't know when it was replaced last. If that doesn't help, she'll have to find a mechanic back home to do O2 sensors

 

[wardriver]

Hit it 2 twice with a 1/3 can of seafoam down a vac line before you do the plugs....

 

[oceanside78]

Where's the vac line I need to use? And do I just poor it in? I have some but it's liquid

 

[oceanside78]

Are fuel filters/plugs/wires a pain on these or a pretty simple job?

 

[awpsome]

fuel filter not to bad, except flare nuts come in handy..
also some penetrating oil helps the night before if it hasnt been changed for a while..

spark plug wires is very easy, just remember to mark which goes where and remember to put it back the same when you replace it to the new wires.

plugs are pretty straight forward as well, usually hardest one is driver side towards the back.. it wasnt to bad for me cause i had the tools that would help make it easy for me to get around certain parts of the engine bay. but others found it more easy to take out those parts that get in the way.. sorry to sound so vague, i dont remember exactly what was blocking the spark plug but i know it was blocking it enough so you cant use a straight extension to get to it.

haha all in all best of luck!

 

[Volley]

Just did the plugs and wires on mine and the driver's side against the firewall is the trickiest per say. I was expecting it to be a pain, but a long extension actually made it very easy...

 

[oceanside78]

just did it. fuel filter was the biggest pain IMO, the thing kept trickling the slightest amount of fuel. Got it though. runs much better. Lets see how the MPGs do

 

[the great him]

if you replace the o2 sensors only do the front one, the back one really doesnt do much and even if its bad it wont affect how the truck is running, all it does is monitor the cat and tell you if your cat is working. the front o2 sensor is the one that will control how your motor runs.

where are you deploying to? army, navy, marines, chair force?

seafoam will go into the intake just make sure you find a vacuum line that goes to the main body of the intake, not just one cylinder... you can also run a can of seafoam in the fuel tank... that will help clean out your injectors good luck man and stay safe!

 

[JohnsD90]

Plugs and wires could definitely help.

Yeah they are supposed to help, but even after my clogged and backwards fuel filter cahnged, mice nest in the airbox removed w/new new filter, misfiring plugs and wires changed, and an oil change change i saw no difference in mpg and a slight increase in power, but i was getting 20mpg beforehand, and i did not drive it harder.

 

[oceanside78]

if you replace the o2 sensors only do the front one, the back one really doesnt do much and even if its bad it wont affect how the truck is running, all it does is monitor the cat and tell you if your cat is working. the front o2 sensor is the one that will control how your motor runs.

where are you deploying to? army, navy, marines, chair force?

seafoam will go into the intake just make sure you find a vacuum line that goes to the main body of the intake, not just one cylinder... you can also run a can of seafoam in the fuel tank... that will help clean out your injectors good luck man and stay safe!

thanks for the heads up

Army btw, closing out Iraq

 

[the great him]

thanks for the heads up

Army btw, closing out Iraq

well good luck and hope you enjoy being bored... whats your MOS, how long you been in? 11b here, just got back a year ago and while i enjoyed it now looking back it sucked balls while i was there, so boring so many stupid rules -just typical army BS -its not a war, in war you can shoot bullets, not throw chem lights and 12 steps of EOF...

 

[jeeper1]

To all the service men and women on here, Thanks for serving and for sacrificing your time away from your family and loved ones! My grandfather was retired army and I have 7 uncles that are retired army and an uncle that is a retired admiral in the navy.

 

[oceanside78]

well good luck and hope you enjoy being bored... whats your MOS, how long you been in? 11b here, just got back a year ago and while i enjoyed it now looking back it sucked balls while i was there, so boring so many stupid rules -just typical army BS -its not a war, in war you can shoot bullets, not throw chem lights and 12 steps of EOF...

11B here as well. Iraq is picking back up man. They are trying to get the last hit before we leave. 5 dudes just died last week. They are trying to show the community that the reason we are leaving is because of they are hitting, basically taking responsibility for why we are gone. The general public doesnt realize whats really going on.

But I have 800 GB of movies and 15 lbs of protien powder for the bordem :thumb3: