Alrighty, 116k miles, oil just changed, and im getting about 16 MPG. can anyone give me some clues to why this may be? thanks!

 

Tire pressure, air filter, fuel filter, spark plugs, drive too fast, commute too much, 02 sensors, coil packs etc. etc.

Have you checked your air filter and spark plugs, as well as tire pressure?

 

how about knock sensor?

 

I don't believe the KS affects fuel economy.

 

it does....I think I get about the same mileage because I do way too much city driving. The auto tranny sucks up a lot of gas if you gave a heacvy foot. A lot of stop and go doesn't help mileage either....

 

tires are at 36f 32r, brand new k&n panel filter, no idea on plugs, probably about 3 years old... drive about 10 miles a day in city, hardly go WOT, filled it to half yesterday and already its almost down to a quarter(i know gauge is a POS, but still that much in a day....) could it be O2 or KS? i read that when people replace KS it feels like a totally different engine. do either of these throw ghost codes? ive got no CEL so im wondering if that may be the case. thanks for the feedback so far though

Edit: hector if youve ever been to rockford you probably know stop and go is all we get here... they need to revamp their stoplight system...

 

You also might want to add a bottle of Chevron Techron to your gas to clean the fuel injectors, run some SeaFoam through the brake booster cable and clean your TB and IACV. Check your PCV and EGR valves per the Haynes manual as well.

 

If its 02 sensors you should have a CEL. There is no CEL for KS.

 

Even though your CEL is not lit, the ECU might have stored a code for the KS - go ahead and check the codes. If the ECU thinks everything is fine, you'll get 0505, if there is a problem with the KS (or the KS harness), you will see a 0304.

 

change sensors and plugs, if you already done the filters.. i doubt knock sensor does anything to fuel economy but hey what do I know.

keep in mind, stop and go really make a difference on an old 100k+ auto cars no matter how well you maintained your car.

 

alright thanks guys! ill look into that today. 1-10 how hard is it to change sensors?

 

O2 sensors are easy -> 2
KS is easy once you have the right tools (see the stickies) -> 3

 

0505 does that mean nothing is wrong?

 

Per Haynes manual - 0505 = no codes identified.

 

Thats not how you determine your fuel economy.

Fill the tank then reset your trip meter to zero. Drive until the tank is down just about empty then fill it up and look at how many gallons of gas it took. Then divide the miles you drove on that tank by the gallons of fuel it took to refill and you'll get an accurate MPG.

 

Read this FAQ: http://forums.maxima.org/showpost.ph...6&postcount=38

 

IT could be that the combination of stop and go traffic with an auto tranny is causing your problem. I've got a 97 auto with 85K on it with the K&N panel filter and it runs fine. My commute is often times in traffic that you would swear would be faster walking. And I often like to accellerate a little faster than I need to. I'm also running 225's for tires which I'm sure doesn't help either.

I have seen my mileage as low as 200 miles per tank and had a lot of the same concerns that you do until I took my first road trip where I was able to put on almost 500 on the road (roughly 31 MPG I believe).

Let us know what kind of results you get on any of the suggested remedies.