So i have been getting awful gas mileage lately. I thought it was my aggressive driving at first but I have been monitoring the mileage i get per tank and it usually never breaks 200miles for the WHOLE 18 gallon tank. Thats around 12mpg which is WAY too low compared to what it was a couple of months ago (around 23mpg).

I have changed the filters. Brought it to a mechanic but he found nothing wrong with it but still it guzzles. There are no codes being displayed either. Very annoying, I now cut back on long trips and it just doesnt seem right. the long roadtrips are the main reason why i love my maxima so much.

Any suggestions on whats going on? It would be GREATLY appreciated.

 

what year is it? it could be an array of things depending on what engine you got

 

It could be your agressive driving along with other things.
Anything significant changed "a couple of months ago"?
How do you know you get 200 miles with 18 gallons? Do you run your car until it runs out of gas? (give more details on your calculation, method, etc.)
Is your engine running nice and smooth (no rough idle or misfire)?
When was the last time you changed your spark plugs?
Which filters did you change?
"Codes no being displayed" means no SES light on dashboard or no codes after hooking up a scanner?
Proper tire pressure is also a factor, are they properly inflated?

 

pretend it's a v8!

j/k something is seriously wrong with it. I'm guessing you have a vq30 and a bad knock sensor, because you have no codes and bad mpg.

 

my driving style has never changed. i used to get decent mileage even before. from what i can tell, engine runs just as smooth as before.

its a 2000 maxima gle. 80k miles.

i change the oil periodically, and the air filter was just changed.

car was bought with 68k miles, i have not changed the spark plugs (not sure if they have been changed at all). I thought you only have to change them every 100k

the 200miles/tank is a close approximate. I reset the trip odometer with full tank and didnt fill the tank up until it was almost empty (i had done 180 miles when gas light turned on). the running low sign comes up at around 3 gallons since a full tank refill was about 14.5 gallons and the tank, i believe is 17.5 gallons in volume.

I drive mostly on highways. Last year i did a round trip from boston to NYC (~500 miles). The tank lasted to about 20 miles outside of boston (480 miles). so the change is undoubtedly drastic.

yes, i hooked the car up to ODBII and no codes.

i always maintain my tires to at least 30psi.

I should have added that, before this problem, the car had problems when idle. The rpm would drop at random occasions while stopped for a long period of time (red lights) and the engine would ultimately shut off. I would have to restart the engine and give it a quick tap on the gas pedal in order to keep the rpm from dropping again and it would be fine afterwards. I checked with a reputable mechanic and he said he was unsure but his guess was a faulty IACV. however he recommended that i keep driving it and see if it got worse. it did not, in fact, i have yet to encounter that problem since (which was very surprising).

But, this new beast popped up and i hope i have shed more light on the matter.

thank you all for your time

 

Hmmm...almost sounds like a fuel leak somewhere. Do you smell gas at all at start up or when you shut the car off? You might want to do some thorough odor checking around the car when it is idling.

 

knock sensor.

 

MAF alert!

I just increased my mpg by 50% by breaking out the old maf and cleaning it. The one that was in there had corrosion on the metal from moisture. Yours is probably just old and dirty.

 

Oh yes...duh...forgot about the MAF as it has been a while since I've had an issue with mine.

Can try cleaning it, but probably best just to replace the sensor. The sensor can be had from Dave Burnette.

 

I have the same problem with my vq35, I actually get like 24-26 mpg on the highway but in the city I only get 11-12 mpg, I can't figure it out

 

same here, i get a good 18-20 on the highway and about 10-12 in the city. It pisses me off, i try and save for mods, but the money just keep flying off on gas. but im thinking its my cats or pre-cats( btw do clogged pre-cats give off a rotten egg smell?) idk what else it can be, i have yet to check for code, no ses thou.

 

change your fuel filter i had a cadillac and it was doing the same thing idling erratic and i found out it was the fuel filter .You wouldnt believe how much better gas mileage you will get.

 

Me I get like about 215 miles on a full tank like 85% city 15% highway and a little better now with a intake!!

 

You all need mafs! Horrible MPG all around!

 

Well most of this stuff sounds all too familiar and my 01 has about 85k on it and I'm getting about 275 with city driving and some freeway on a full tank of 92 octane if I'm lucky...
Gonna buy some new plugs and a air filter but I'm thinking after reading this I'm gonna at least have to give the Maf a cleaning maybe a SeaFoam and a oil change. I started hearing a funny noise sort of like a baseball card in the spokes of a bike in low rpm's in first gear...Hope this will help aid...

 

ding!



sounds like a MAF sensor problem and from what i have seen, they won't throw an SES light....


could also be intake manifold leak, unmetered air will make you car run pig rich

 

Change the following;

1) Fuel filter
2) OEM Plugs
3) If you didn't know 2000 coils are all f..edup. Replace them with OEM 2001 coils all around, don't pick and choose. This is big ticket item.
4) Change O2 sensor and MAF sensor -- O2s are big ticket items, I bought mine from www.ngk.com
5) Get alignment done if the car drags
6) Tire pressure in cold weather is 36psi period. 30psi is a joke, I put 38psi to get 24MPG in CA.

 

im starting to have similar issues on my 03 se. not nearly as bad as 200 per tank. but down from 25-27 mpg to around 19-21 all around. 100k miles, occasional p0328 knock sensor error.

anyone eve buy from this seller?
http://cgi.ebay.com/ebaymotors/New-N...Q5fAccessories

 

something is very wrong.. even if you were to drive around the city and floor it at every opportunity you get.. you should still be doing way better than 10-12mpg.. thats just crazy

 

I'm not arguing this, but the car is rated for 33 PSI on the front and 30 PSI on the rears.

Of course, a higher pressure will improve your gas mileage, but you will see a decrease in traction and smoothness of ride will suffer as well.

 

Alignment issue?

 

CRC makes a MAF cleaner, essentially you remove the MAF spray the crap out of it with the cleaner being careful not to let the straw touch the MAF. Allow the MAF to dry before reinstalling. If the milage increases but then goes back to the horrible numbers, get a new MAF.

The 2000-2001 Maxima MAF is less expensive than the 2002-2003 MAF.

 

MAF sensor was cleaned with CRC two days ago..the most notable change was more responsive acceleration, especially in the 3-4 gear on highway.

I hadnt thought about this alignment issue but it is definitely what I will invest in next. I kept pushing alignment off and its definitely needed. I cant take my hands off the steering wheel for more than 2 seconds without it drifting to one side.

 

drifting is usually caused by tires, although if the caster is out ( not adjustable on our cars ) more than 1 degree it will pull to the side with less caster.


just some food for thought

 

I'd say take your car to a smaller alignment and frame shop. See if you can get a free diagnosis and get them to tell you what part needs replacing. Then when you pick up the car just say you are between paychecks or have to pay some bill and can't afford the repair right now.

 

I'd say knock sensor. How does the car drive? Sluggish? If so, then this may be your problem. Buuuttt..I'm not all too familiar with the knock sensor problem on the 5th gens. I know its a major problem on the 4th gen.

If it doesn't drive sluggish..theeen proceed to other options.

 

car drives VERY smoothly actually, i doubt there's anything wrong with the knock sensor. It has never been sluggish, very slight sluggishness when I was using 87 octane rating for 1 week but with 89 it runs like a champ.

 

If you are on original coils, I would spend my money on getting 6 2001 pack coils (not from Ebay) from Dave Brunette.

By now you O2s would have fouled up with improper ignition and fuel burn. So no matter what never replace the O2s before replacing your coils (offcourse NGK plugs go with it).

Go step by step, it has been documented well that 2K have messed up coils. BTW, I replaced my coils at 65K will 2k1 coils and haven't looked back -- now at 180K.

 

Im having the same problem on my 2000 maxima. I get around 14-15mpg city and its not aggressive driving either, i always put premium gas in. I recently changed the spark plugs and air filter so I don't know why mines so bad either. Is there any way of knowing if the MAF was changed in the car's history? Ive only had it for about 20k its at 112k now. Btw on the maf there's a bright green dot on the top is that anything or?

 

Start from replacing your O2 sensor - the one on the exhaust approx in the middle of the car. I was having similar mileage and replacing it took care of the problem. Car never thrown a code about O2 sensor and was showing steadily increasing HC content on emissions tests while still passing them. Eventually I got annoyed enough and replaced O2 sensor (~$60 OEM IIRC) and was stunned with mileage increase. It turns out the sensor was not so good from the day one and it was slowly getting worse. I'm getting 23-24 mpg hwy driving nowadays. Another thing which kills mileage are the short trips (5-10 minutes) with few hrs in between in a cold weather - car doesn't have time to go into so called 'closed loop' and use its O2 sensor so it doesn't really matter whether it is good or not - you still get horrible mileage.

 

the search for idle is normally the sign of the maf sensor malfunctioning.

It will be REALLY bad before it sets of the mil. So im as sure as I could possibly be that your maf sensor is bad just not bad enough yet.

Now all things considered that might not be everything. When youve got things out of tune it can be a couple things. What id think about next is the actual o2 sensor