I have a 1998 max gxe with 85k (50miles). I've changed the plugs, the fuel filter, air filter, oil filter, trany fluid, and muffler, but i'm still getting the worlds worst fuel economy. I get about 150 kilometres (100 miles) off the first half of the tank.

I've taken it to the dealer and let them run some tests but they said that everything is okay.

Does anyone have any suggestions as to what might be the cause.

 

try pulling your codes to see if you have any sensor showing up...check your tire pressure...are you running 93?....do you drive it hard? even so that seems really low...

 

remmeber to check your knock sensor and O2 sensors....and guy the knock sensor is a ghost code, it only appears when you pull the codes out...and One time my O2 whas not tighting enough...and my fuel economy was very bad...i check it, reintalled, and everything was right.

remove your O2 sensor, spray a little CB cleaner...on the O2 sensor, right and left bank. And clean your KS harnnes...maybe sometimes theres a little dust.

 

If you do a lot of short trips without letting the engine warm up before driving, the fuel economy will be poor.

 

The tire pressure is fine, and the car is driven hard but like you said, i should still be getting more out of my tank. What else could it be?

 

I don't why your mileage is that bad, but one factor can be the quality of gas in regards to winter (oxygenated) vs. summer fuel. Here in Oregon, we've had the crap gas for the last 4 months and my highway mileage dropped from 500 miles per tank down to 400. Recently, we've got back to the good stuff, as it's back up to 500 miles per tank (highway). I thought something was wrong when the highway mileage went from just under 30 mpg to 23.5 mpg. That is nearly a 25% drop in ecomony. Even at that rate, you shouldn't be as bad as you are now. Hope that helps.

 

My mpg isn't that bad....but mine is low too. I only get 240 miles to a tank....although I drive pretty hard and mostly city miles. I'm getting the knock sensor code, but it's a ghost. I ran ohms checks on all the wiring, harnesses and the sensor itself....it's okay. I must have a loose, dirty or fried O2 sensor....just haven't had time to deal with it....

 

but if you are getting the code then your timing is getting retarded...hence the 240 miles/tank......

 

Exactly..... Sh*t....I probably won't pass emissions....

 

Replace your front left O2 sensor. I went from 248 Miles a tank to 347, 100% city driving. On a recent roadtrip I got 433 miles on a tank driving on average 80 mph. I changed the plugs, air filter, Oil and cleaned the throttle body. The biggest kick came from the O2 sensor change.

Regards,

 

With Shell Gold (91) I get at least 500KM a tank city driving. I usually refill when I have about 5 litres of gas left... But that's always over 500KM.

 

have you cleaned your throttle body?
if not then....
http://www.motorvate.ca/mvp.php/517

 

I'm currently at 76,000 miles....at 60,000 I replaced the fuel filter, plugs, did a TB cleaning....etc.

What happened was I overheated back in December and that's when my knock sensor CEL started popping up. I think I cooked an O2 sensor.

 

I have a 95 at 76,000 and only get 220-240 on a tank, replaced fuel filter, air intake+filter, TB cleaning and hasn't gotten much better, can't use more than 91 octane in Cali though, don't know what else it could be.

 

measuring half a tank of gas is inaccurate because nissan fuel gauges are notoriously inaccurate. Try a full tank of gas and measure untill the gas light comes on.

 

what do you all consider a tank of gas??? i only get about 280 miles "to a tank" but i usually fill up somewhere between a half and a quarter tank. I'm avg about 21-22 mpg which im content with. I know in the winter i was doing all town driving prob no more than 3 miles each way and i was gettin around 15 mpg. so theres more to it than just saying you have bad gas milage.

 

you don't need to look at the needle, just start with a full tank, measure the mileage and the amount you put in, then you should know exactly how much mileage you are getting regardless of how much gas was already in there

 

I would consider a tank of gas to the point where it is just above E, or roughly 15 gallons, which last time I filled up gave me 15.8MPG even though I replaced Fuel filter, air intake and filter, cleaned TB

 

In my mustang, when I go through a few high revs and races, I get 14 mpg and I have a v6! I know of some GT's that get better milage then me, its pathetic.

 

yeah, even o2 sensors that don't trigger any codes can be screwed up or not working "up to spec." My MPG has been going down steadily the last year or two, just finally bought both front O2 sensors ($67 or so at thepartsbin.com shipped for Bosch OEM spec) and installed them. Mileage seems a bit improved, I'll give it a few weeks first...

 

Who are you talking to?

If it's me, I don't measure 1/2 a tank...I GET 240 MILES TO A FULL TANK!!!!.....

 

Anyone have any instruction/pictures they can post on how to replace
the O2 sensor. My knock and Oxygen sensor needs to be replace and I
have no clue where the Oxygen sensor are located. I don't want to fill
up my tank every weekend and get 250 miles out of it. I drive in the city and I don't drive hard.

Some instructions on how to replace the sensors will be greatly appreciated and the tools need to get the job done. I'm a new owner to a 1996 Maxima and I want to learn more about fixing my car. :-)

 

Your local autozone can rent you out a tool to remove the o2 sensor for basically free. You give them the value of the tool and they give you the money back when/if you return it. I think they give you 48 hrs to use the tool and then you have to keep it if you dont return it before the time given. Just jack up your car and you should be able to find the 02 sensor somewhere on the exhuast pipe if im not mistaken.

 

First of all.....there's three O2 sensors on a 1998 Maxima/I30....the left bank and right bank and post-cat. Here's a diagram...

Second....it doesn't take a special tool....just a cresent wrench and some finess.

 

Thank you "DJ E-Bam" for the diagram. I was planning the change the Knock Sensor myself. With the diagram you just provided, I might want to get a ramp and change the 3 oxygen sensor also. I have a 1996 Maxima and I want to know if its hard to change the oxygen sensor for someone with no mechanical background? If is just a simple unplug and plug, than I'm up for the job. Any feedback and tips on the installation of the sensor will be greatly appreciate. Just got my car more than a month ago.

_______________
1996 Maxima GLE

 

The tricky part about the 02 sensor is getting it off. A crescent wrench may round the corners, "stripping" the nut. You may need some liquid wrench, depending on the amount (if any) of rust holding the nut in place. Some are really on there. The 02 tool helps because it is, in effect, a socket that can more easily grip the nut. It does not take too much expertise if you know how to loosen and remove the nut, then follow the wires to the harnes to plug and play. Make sure you fasten the wires back, as they were originally.

 

Once the 02 sensor are in place and tighten, do I need to reset anything? or any adjustment to the engine before the engine light turns off? Or the engine will turn off the light once the sensors are up and running?

_______________
1996 Maxima GLE

 

reset your ECU

 

I've always used cresent wrenches and never had problems. You just have to use the normal amount of care....like anything when you're working on a car. Although, I do recommend using some DeepCreep on it first.

IF NO ONE HAS EVER HEARD OF OR USED DEEPCREEP....BETTER RECOGNIZE FOOOO!!!!

 

I'm having the same problem. I used to get @ least 350 in the city, now I only get about 240 if I'm luck. I did a complete tune-up with nissan and still having the same problem. Any suggestion?

 

Replace your 02s first and see if your knock goes away..alot of times it piggy backs with other codes...and is only really bad if you get the code by itself...

 

O2s...O2s...O2s.....