Hey guys, I'm new to forum. I did read your message about using the search feature, but for some reason it won't work for me(even on the test site). So, here's the question:

I've got a 92 SE with about 118K on it. Recently, my gas mileage has gotten really bad... like down to 15 mpg in the city and only 24 mpg on the highway (I used to get 27 or 28). This has happened on the last several tanks. The car seems to be running fine, with an even idle and such. Any ideas on where all that gas is going?

Thanks!

 

Did you switch the level of octane of the gas you are using? I noticed that i went from 18mpg to 15mpg when i wnet from premium to regular, so i switched back. then my highest so far has been 23mpg after a 100mile rountrip and an oil change. We'll see how this week looks pretty soon. I will let you know if it is still over 21.

Brian

 

nah- I've always used premium gas in the car...

 

after searching forever, i finally found out why i was getting crappy gas mileage. replace your O2 sensor. i just replaced mine this past weekend, and i cant tell you the difference it made. i was probably getting 14 mpg in the city and now im probably getting 22 mpg city. no joke. the sensor can be pricy...about $100 from cragen and pep boys but you can find one cheaper online. hope this helps.

 

it could be the spark plugs...replaced mine and everything went dandy after that.

 

If it's the O2 sensor it should have thrown a code in the ECU. But that's the most likely culprit.

In most cars if the O2 sensor goes bad the ECU goes into a full or super rich mode to make sure the engine stays together.

 

the o2 sensor never threw a code in my ecu that i know of. how can you tell if its throwing a code?

 

Thanks! I will try replacing the sensor... however, is there a way to check for a stored trouble code first? That is, I don't have a scan tool, so I'm wondering if the Maxima has a "self-diagonistic" mode or something like that where it would flash the trouble code through the MIL (my Jeep Grand Cherokee does this if you turn the ignition key on and off three times)?

 

As stupid as this might sound, but did you ever try using fuel injector cleaner? Beleive it or not, my car (92Se 5spd) was barely getting over 220 miles to a full tank. Upon using Gunk fuel injector cleaner, I got 331 miles out of the very next tank. I never thought that any of those cleaners really did anything, but I was proved wrong. Now, I add this to my tank once a month and my mileage has not decreased since I've started using it (about a year now). This would be the cheapest thing to try first. As far as the 02 sensor, look around and avoid Pep Boys(they'll rape you). I found mine at another store for $65. Mine never through a code either. I accidently put this same reply to a post about steering wheels. Stupid me.

 

Wow- thanks for that idea. I'll try the Gunk cleaner first, then the O2 sensor. Who knew that it would make such a difference?

 

I hope that it works as good for you as it did for me. But for less than $2.00, how can you go wrong?

 

go easy on that injector cleaner stuff. it's gonna eat away the metal on the injectors and then you might have a problem with running rich. once in awhile is ok. (don't quote me on this though, i remember reading a thread about fuel injector cleaners awhile back)

also, you might want to check your tire pressure and air filter. under-inflated tires can hurt your gas milage. make sure all tires are up to specified psi ratings. same as with the air filter, besides losing some power, a clogged filter will also hurt your gas milage.

 

Before paying a little more and spending the time replacing the O2 sensor i would replace the fuel filter. I got my '93 SE last year and just replaced the fuel filter a month ago. this got about 12 bucks and was super easy to do, literally just loosen the hose clamps, pull the old one out and put the new one in.
you do have to relieve the fuel system pressure first, you do this by removing the fuel pump fuse, then start the car and run till it stalls. then you turn it over a few more times. Now you can remove the filter but have a rag under it and a container handy b/c it still has gas in it and it could be a mess. Be aware that the fuel filter has a specific input and output which is labeled as an arrow in the direction of flow. This is all in the hanyes manual if you have one.
I already used fuel injector cleaner but this jumped my milage from 23 to 25mph, all hiway driving. hope this helps, it's really simple everyone should do it as a matter of maintence.

steve
'93SE pretty much stock b/c i'm poor!

 

Try new fuel filter, plugs if they are due, PCV valve and check the EGR valve for proper operation.
http://www.cybrrpartspro.com/Chilton...961m/8961.HTML

 

It could also be bad gas. I got ahold of a really bad tank of gas and it was even 93 octane. I got about 230miles to that tank instead of 330 or more. If you are gonna use injector cleaner, I reccomend STP or Barryman's B12.