Colonel

I have been having a mileage issue as of late (started prior to the "oxegenation" fuels). I can barely get 20 MPG with 98% highway driving. At first I thought, hmmm driving style. But I have gone many weeks driving like a grandma AFTER reseting the ECU.

Some facts:
* I NEVER put in anything short of 93 octane
* I have NEVER used a "fuel" additive (manual says not to and I have heard Nissan injectors are very sensitive)
* I really only use one gasoline at a specific station.
* No engine mods.
* I use AmsOil synthetic 5W-30. Changed out at 3K (sorry Bill have to until warranty runs out. I dont even want to start that argument with Nissan OR the .Org.)
* I use a Mobil 1 1-110 filter.
* I have changed out my air filter before this experiment (Nissan OEM)
* The car has 23850 miles on it.
* My tranny fluid (manual) was changed 4,500 ago and I have checked it twice for proper fill. No problems.
* I verify the air pressure in my tires twice a week, sometimes more since the temp fluctuates so much.

I am stumped.

The other day I started the car and went to the trunk to get my scraper and noticed that the exhaust smelled very heavy of gas. I know that when you first start in the cold it runs rich til op temp. But I dont remember it smelling THIS strong/bad. And I dont let it idle for more than 1 minute or 2. Just enough to scrape the windows get in and drive.

I dont notice any engine hesitation, no CELs, but my MPG is awful. Sometimes is seems to lack power, but that could be a mental issue. I used to get in the range of 25+ MPG with aggressive driving. Is this an indication of Coils/something else?

DAVEB

iTrader: (133)

I think there's a bad gas mileage TSB. I don't know which Maximas it covers, when I get a chance go get it & let you know what it says. I think my car is doing the same thing!

Colonel

ooooommmmm I appreciate that a bunch oh wise one. I say for sure this one has me baffled. Hopefully it will apply.

Quicksilver

iTrader: (1)

Bad O2 or cat is what it really sounds like, but no code is kinda strange. A bad cat would have other side effects, come to think of it...maybe just an O2 sensor.

Colonel

That is what I thought too, but no codes = If an O2 was starting to fail, should it not store something?

UCF_94lude

I would definetely like to have that too! I have bad gas mileage also.

One other thing, when I got gas the other day, my dte setting claimed I had only 30 miles or so left, but I was only to put in 15.1 gallons on a 18.5 gallon tank?

xfirepwr1

18.5 gallon tank?
My max has 17 gallon tank last time I checked

jjs

Where did you check?

xfirepwr1

Every time I fill up when Im on empty I can only put in lik 15.5 gallons. I really dont think I have 3 gallons left in there when my dte says 21.

jjs

All 5th Gens are 18.5. User manual page 9-2.

I would say these new trip computers on the cars just plain suck. Give me old analog gauges and warning lights any day.

UCF_94lude

It says US Measure, 18.5.. and Imp measure 15 3/8. What the heck does that mean?

jjs

http://gocanada.about.com/library/howto/htig2usg.htm

Quicksilver

iTrader: (1)

Well my CSVT ate O2 sensors every year I owned it, but I never once got a code. I could just tell by the smell of the exhaust. If it smells really gassy or like rotten eggs, then it's the O2. If the engine has problems pulling (breathing, so to speak), then I say it's the cat. Since yours only has the gassy smell, I say it's the O2...even w/out the code.

IceY2K1

iTrader: (3)

How cold is it there? I average 23-24mph highway SINCE NEW, so yours is not that bad.

When it is cold out and you first start your engine, the ECU stays in OPEN loop longer, which if you make lots of short trips could effect your mileage. However, if you log 98% hwy miles I doubt that is your reason.

Colonel

I had a 95PGT, so I know that feeling..ROFL. I got codes on the Probe, but this one is a tad different. I would hate to just start replacing O2 sensors at $80 a whack. Although I have a ESM, so I guess I could DVM them and see if they are in spec.

Yeah, I know it does that...but I have not noted the smell of gas before. Plus its a bigger dip since roughly October. I thought it was driving style, but the extremem presence of gas in the exhaust is a huge question mark.

DAVEB

iTrader: (133)

False Alarm! It wasn't really a TSB- Just generic "helpful hints"- a bunch of obvious stuff about driving style/weather etc. We're starting to have problems with 5th gen coolant temp sensors, it might something to look into.

Quicksilver

iTrader: (1)

Damnit Dave! You're no help! J/K

CHAZMAX

[QUOTE]Originally posted by xfirepwr1

Every time I fill up when I'm on empty I can only put in lik 15.5 gallons. I really dont think I have 3 gallons left in there when my dte says 21. [/QUOTE

Believe or not, I think it actually does hold 18.5 gallons. This use to pi$$ me off also. So one day I drove and drove... It has AT LEAST 3 gallons once it's "approximately" on "E". I've done this several times now.

As far as the computer goes... It's just a temp guage. That's all it's good for. Nothing more, nothing less.

maxima00

i have good highway miles and all...but i do smell gas sometimes...what could that mean>?

Colonel

Coolant sensors....possible causes/symptoms noted?

Well, here is something else I was thinking about. 5th gens have a "lifetime" sealed fuel filter [yeah right...lifetime what bs]. I am used to changing this out on normal cars once a year. Is there a possiblity that the fuel filter could be to blame on this one?

DAVEB

iTrader: (133)

The coolant temp sensor is a variable resistor that tells the ECM what the engine temp is. If the resitace values are out of range,
(too much resitance= too rich, not enough= too lean) the ECM won't be able to determine the correct fuel mixture. About the only thing a fuel filter can do is get clogged- then you starve for fuel!

Colonel

Would it be to much to ask if the acceptable parameters are in the ESM? If not where would I get those values?

DAVEB

iTrader: (133)

They are in the ESM. In the "quick reference" section, I think.