I recently bought a 98 Maxima, I drove it for about a week and realized that I take too much gas. It take 12-13 mpg in the city and 18 mpg on the hgw. Is the something wrong with the car or something. and also what factors underthehood effect gas consumption. Thanks btw I just replaced the airfilter

 

Check for a knock sensor failure code 0304 in the ecu. This failure would also be accompanied by a really flat power output, as some have said a 4cyl Honda will tromp on you if your KS is bad..

 

- Full tuneup (oil change, spark plugs, PCV valve, air & fuel filter, and TB & IACV cleaning) - Look at the "how-to's" thread at the top of the forum
- Make sure all your tire pressures are the same (put all of them to 32)
- Use premium gas (use the Chevron with Techron Fuel System Cleaner found at auto stores or you can use the BG44k Fuel System Cleaner found at some car dealers like GM or Ford or some other ones)
- Replace front O2 sensors
- Replace knock sensor

 

Stop redlining it! j/k. Follow what Jatan said..

 

If he rides with 32 psi in his tires his gas mileage will suck. It really depends what tires he has. It says what max psi the tire should have and to fill them very close to that. My tires are 44psi max, the fronts are only 35 or so and they look flat...

 

Well stock psi is 29 so I think he should keep it at atleast 32

 

thanks for the assistance do you have any quotes about how much that tune up would cost

 

Buy the parts (use NGK plugs) and do it yourself http://forums.maxima.org/showthread.php?t=254238 and in the end you'll feel proud

Or you can check the Regional forums and ask someone near you to do it (but you can do it by yourself, not too hard)

If you have money, buy NGK platinums, but if you don't want to spend that much on platinums, buy the copper ones http://maxmods.dyndns.org/?MaximaSparkPlugs

 

stock psi is 29 but that's only for the tires the car comes with from the factory...

 

Would a CEL tell if the knock sensor is bad? I'm new so I'm trying to get as much info as possible

 

no, disconnect the knock sensor and see if the car feels/drives worse. If it does the KS is fine if there is no difference hten the KS is shot...

 

If he keeps his pressure at 32psi he should get what Nissan says he should get for mileage. I run mine at 32psi and I have seen as high as 27mpg on the highway. The tires would have to be just about flat to drop from mid 20's to low teens in mileage.

Running your tires harder than Nissan recommendation will improve your mileage somewhat, but will sacrifice some ride quality and *potentially* some handling, depending on the tires.

 

The KS is a ghost code. It will not turn on the CEL by itself. If it is bad, you'll have to check the ECU for codes by yourself or use a multimeter to test it. Get a Haynes manual since it'll be very helpful to you now and in the future

 

Original nissan tires taht come with the maxima have a max psi rating of 38 or 40. If his tires have a max rating of lets say 44psi then if he runs at the psi recommende by nissan his gas mileage will suffer. The way you said makes it seem that if he put a tire with max psi rating of 100psi, he should still run 32 psi cause that's what Nissan says. You have to adjust so that the tires are perfectly flat with no bulges on the sidewalls. Like I said before I have mine at 35 psi or so and ther bulges are quite big. As soon as I put it at 40ps1, max rating is 44, the sidewals ahd very minimal bulges...

 

Doesn't it take longer to stop when the psi is higher? I had mine at 35 all around, but after I got an alignment, PepBoys messed up the tire pressures. I put them to 32 all around afterwards.

Need to go to PepBoys again to have it realigned My rear wasn't seated properly so the alignment was off. Good thing they have a 6 month/6000 mile warranty

 

Non-specialty tires (OEM size and rating) should be very similar to the tires Nissan OEM'd when the car was built. If you choose to run a different size tire with a significantly different pressure requirement then you may have to run 50 psi (or whatever) to get the correct performance. The original post did not mention anything about tires. I'll stick with my original comment, somewhat re-worded: If your tires match the factory size and rating, going with factory psi suggestions will result in factory levels of tire-related performance.

Unless you have rubber bands for tires, you should have a small bulge at the "bottom" of your tires. But... the shape of the sidewall is not useful for checking tire pressure. A correctly inflated tire will have a flat contact patch and will wear evenly across the tread. Under-inflated tires will wear excessively near the sidewalls, and over-inflated tires will wear excessively in the center of the tread. You can be well within the tire's psi specs and still be over-inflated.

I think it's time to drop the tire pressure discussion. If tire pressure was low enough to cause a 50% reduction is mileage then he would probably have ruptured the sidewalls on very short order. Or cut through the rubber because the rims are riding on the tread.

 

there are 2 different ratings for the tires you have JATAN, one has a max psi of 44 and the other of 35psi. I don't know which one you got but whatever...

 

I've never read such mis-information on tires is my entire life ! My manual says 33 front & 32 rear (215/60/15 '95 Max). It's entirely up to you if you want to run harder, just watch out for uneven tire wear and a bouncy ride.
The 44 psi you guys are talking about is the maximum pressure that should be used. This is normally only used when installing a tire and should never ever ever be used on a daily basis. Bad things can happen, you guys can figure that part

 

Like I said, inflate the tires so that you have minimal bulging on the sides. I had mine at 35 and it looked like I had a flat tire. Put it up to 40 and it looks almost Ok. I want to see where this MISINFORMATION is...

 

Keep the tires at or above the stock psi... lets leave it at that

The guy at the place where I got my tire balanced told me to keep it at 35 in the summer and at 32 in the winter

 

Are you sure it's not 32 in the summer and 35 in the winter? They expand more in the summer because of the heat so it would make sense of them to be less inflated in the summer...

 

well thanks for the assistance i just did a tune up I changed the PCV valve, spark plugs ,the fuel filter and the air filter , I couldint change the O2 sensor because I dont have a socet for it so ill go to AutoZone or Straus to get it tomorow well the car starts but this guy was telling me that the PCV valve I got is not the right one so I lose some air when idling and gear so I got to go to Nissan and get their PCV valve from there, Any onve got any suggestions on that, Realy apretiate it

 

1. check and replace the KS
2. Check and replace the O2 sensors
3. Clean DIY the TB, IAC
4. Replace your fuel filter, plugs, pcv
5. tire preassure.

after all this...welcome to 400+mpg club.