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Help!! Very poor mpg

4K views 14 replies 10 participants last post by  kms1990 
#1 ·
I recently did a tune up on my 2000 xterra that had 135k on it. When i bought it i pretty much could tell it never had one so i bought ngk everything and got it down I also got the fuel injectors flushed. Bad news is im only averaging 11mpg, when im supposed to be getting 15-17 city and 18-19 hwy. I have no idea what else could be effecting my mpg this badly. The Check engine light is on, but i was told by advance auto its a common sensor that gets tripped with the 3.3v6 motor nissan puts in the xterra and frontier. If anyone has suggestions or anything it wud help alot. thanks.

-Alex
 
#3 ·
Yes he did mention something about the knock sensor. Ive only had the truck for a month, so i cant really tell if its low on power or not. He gave me the codes i gotta find them. Is that an easy sensor to replace? But, yes the car runs fine if the sensor wasnt on i wouldnt even notice anything was wrong lol.
 
#9 ·
To the dude with poor MPG. With 135k make sure to get that Timing belt ASAP!
Then make sure you got the right plugs for your X. NGK Platinum tipped! Second might as well get new Plug wires then go ahead and check the distributor inside.
Change all your fluids, the tranny needs to be flushed with a special machine and add some royal purple, just a tad. Motor oil to Royal Purple. Air Filter (not that K&N crap, it opens up the air but also takes in more dirt)
Next pull out your Wheel Bearings and clean them out and the housing and repack them in FRESH GREASE (BOY What a difference it makes!) Get an allignment BUT with 135k your bushings could be worn enough to screw up your allignment right away. Get new bushings. You have to press out the old and press in the new (Get at least Polyurethane)
Shocks and tires. Bilstein or Rancho's and Michellins. This all should get her up to spec.
 
#10 ·
OH>.. Check to see if your fronts brakes are dragging. You might not feel it so much but put the car up and spin the front wheels, they should move freely, if not then you need to get new brake calipers or try to at least clean the old ones, grease up the sliders, free up the pistons if they stuck. If you need to know how ask me.
 
#11 ·
try disconnecting the battery for a little bit to clear that code out. Drive around for awhile, and see what your MPG are then, and check after a bit of driving and see if the code is back,
Disconnecting battery for a while clars codes?

That is why I love this site!:informatiker-big:
 
#13 ·
Yeah the knock sensor is not tripping your CEL... there's another code. If it's an O2 sensor or something like that it could be affecting your mileage. I'm lifted 4", steel bumpers, 33s and I am getting 15.5 mpgs around town and much better on the highway at reasonable speed.
 
#14 ·
Yeah the knock sensor is not tripping your CEL... there's another code. If it's an O2 sensor or something like that it could be affecting your mileage. I'm lifted 4", steel bumpers, 33s and I am getting 15.5 mpgs around town and much better on the highway at reasonable speed.
Likewise: ~5" lift, 33x12.5 tires and armored and I get 13-15mpg city driving.
 
#15 · (Edited)
stock 2000 3.3l with 156000 miles on er highway tread tires 265/70/15s recent minor tune up (new plugs wires and fuel filter and distributor, due to failure not for tune up, and k&n drop in filter)

and fresh fluids (do not flush the tranny unless you know its been done before or the fluid isnt too dark as doing it after too long on old fluid could mess it up a drain and fill with new tranny filter would be more beneficial

i ran pennzoil hm oil 10w30 because a few leaks i had (recently fixed and changed to castrol gtx syn blend 5w30 and noticed a better response and seems like a lil bump in fuel economy, would use full synthetic but dont have the $)

new shocks and accessory belts done, service records show 105k mile tune up done at 117k so i think my timing belt was done and battery

i get about 15.5-17mpg average (depending on how much highway i drive that tank) but even before i did anything to it when i got it a year ago i was getting 14.8-16.7 (depending on highway driving amount) and one tank when i filled at half i got 21mpg best since was 18.4 on a 50% hwy 50% city and usual is between 15.5 and 17.2ish best thing i can recommend you do for this is REPLACE THE FUEL FILTER AND PCV VALVE! that plays a major role in our trucks mpg and power and dump a bottle of regular lucas (clear bottle brown liquid in it when you do that) may also try the diy seafoam in the diy section i used the brake booster vacuum line, here is a link:http://www.clubxterra.org/forums/showthread.php?t=18963
 
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