I know there's hundreds of threads about bad mileage, and I've read through them all, multiple times. Ever since I bought the truck, I've kept track of mileage, I even had a thread asking if someone could be stealing gas out of the truck (don't think so, but who knows).

I am lucky to get 9mpg with my truck. If it is just in town, I get ~8.5mpg. If I do mixed driving, I might hit 11mpg. I am easy on the accelerator, hardly ever get above 2k rpm.

Since I've had the truck, I've done the following:

• Hughes plenum
• regular oil changes (synthetic)
• sct tuner (tried different tunes, no change)
• downsized tires from 285's to stock 265's - properly inflated
• transmission fluid & filter (twice)
• seafoamed (intake & gas tank - twice)
• tried different stations, different octanes, nothing really different
• double & triple checked speedometer to GPS, very close
• replaced front 02 sensor with NGK (did see a jump after that tank, but back to normal following)

Right before I bought it owner did new dist cap, wires, & plugs

Here's my latest two thoughts:

I occasionally get a P1740 torque converter error - could a dying torque converter cause bad mpg?

Would a plugged catalytic converter cause bad mpg? I don't hear a rattle, but the truck seems to be hesitant a lot of the times, then will suddenly take off. I wonder if a chunk could be loose that will occasionally free up and give me a boost. I need to take out the front o2 sensor and see if it makes a difference, but I don't want to drive a whole tank like that to see if the mileage goes up.

 

Yes, the tranny sucks a lot of power out of your engine putting it to the wheels. A proper working trans would benefit mileage.

Also, you could go smaller with the tires. My door sticker says 245s as stock. Is there anywhere else that would say 265s?

 

your TC locking or unlocking would cause a slight dip in mileage.. that is never good.. may want to look into it- it may be a simple solenoid swap to fix you up..

it sounds like you're running rich.. (I'm standing by for fire by mentioning this).. two items can cause that.. o2's, and IAT.. you've swapped the o2's, why don't you give the IAT a shot.. it should be under $20.. it is likely the most under appreciated sensor on the truck, and mostly because (imHo) all the wiz-bang BS that eBay has to say on the matter.. (+500 horsepower!!! infinity on a gallon of five year old gas!!! all for $19.99!!!)..

that IAT has a strong bearing on a/f, and advancing/retarding ignition.. they often (like, most often) go bad w/o setting a code..

sounds like you've tried everything else, so, give it a shot and see.. the TC failing to lock wouldn't cost you THAT much in fuel.. I'd venture a guess it would only cost you 1~2MPG's if you run 60/40 HWY to CTY.. Just my thoughts on the matter..

good luck!!

 

whats a IAT,, i mean where is it located.

 

Intake Air Temperature. Most auto parts places call it an "Air Charge Temperature Sensor." If memory serves, it is located on the passenger side, front section of the "kegger".

Here's a picture from a Jeep forum, it may help (the same engines).


It is the brass looking unit with the wires coming off of it, directly below his finger.

 

Yes sir, that is where she is located.