djipka

iTrader: (9)

I just filled up today and after doing the math I almost got a heart attack. I am getting 12 MPG.
Why do I get that bad of a mileage?
all the filters, pcv valve, plugs and all that has less than 10k on them. Most of them are actually less than 5k.
Is it possible that I got that because of the little gas leak I had? I mean it was small but still. I don't know what to think and where to look anymore.
the last thing I did to the car was to put in it a 95 ECU and a new OEM KS. no codes either.
Please help!

maxboy325

iTrader: (35)

Well first I would start with the gas leak that can NEVER be good, then check for codes.... and that you didnt over torque the KS and it cracked.

tbergma1

I would go through another tank of gas to make sure your analysis is correct.

allensteiner21

iTrader: (6)

to improve mpg driving around slc...i'd get a civic i get about 20mpg and i have 9 miles through town and 16 on the freeway - my daily commute.
i was getting less when i had my heavy 17" wheels on and i lost some after putting in a cai. are you modded?

djipka

iTrader: (9)

the KS is all good. no leak as of today. I will drive like that anyway but I was just trying to get some info in.
I had a thread some time ago about the ECU swap and I had questions about the EVAP system. No one gave me any answers. I feel that there could be a problem with that since I swapped the ECU and half of the EVAP stuff is still on the car even thought the computer does not recognize it.

I drive 3 miles to school and back, and the same with work. I know city driving sucks but 12 MPG?

internetautomar

iTrader: (30)

how long does the car sit when you are at school? at work?
if either answer is over 3 hours, then your mpg is to expected.

djipka

iTrader: (9)

I am at school from 7:30 till past noon. at work it sits for like 4 hrs. What difference does that make?
I have a friend with a 98 and he has never gotten any worse than 17 mpg and that was before the tune-up we did. He drives less than a mile to school and work.

internetautomar

iTrader: (30)

short drives with long periods in between are murder on gas mileage. the car (especially as the weather gets colder) doesn't get to spend enough time (if any) in closed loop mode where it operates most efficiently. It is spending it's time in open loop mode where the car runs richer.

djipka

iTrader: (9)

what about my friend than?

Maxgig

iTrader: (5)

I would check the evaporator canister. Do you have a strong gas smell when you park it? If your canister is bad you will get crappy gas mileage until you replace it.

You should be getting trouble codes for it though. If your ECU change is preventing the codes from showing up you may have a problem there as well.

FallenOne

iTrader: (17)

no codes? KS IS installed properly? id get ahold of a scanner and do a diag of the fuel consumption and burn rate, see if shes running SUPER RICH or something....

klemenz

that's weird.. you been driving it top speed down the interstate every now and then? ha

either that or you just drive it too hard

FallenOne

iTrader: (17)

dude seriously, ive been kinda Bahning it lately and im still getting 20.... and you prolly read my situation already. sometyhing is WRONG.

petro2342

Noticed any problems on idle or car starting up? Any noises coming from somewhere?

wxm

iTrader: (2)

Assume that you have checked the tire pressure. What about the struts & shocks?

J RO 9

iTrader: (2)

i filled up last week and after 101 miles, I filled up. It took 6.6 gallons. That's about 15.3 mpg. Those 101 miles were driven in 2 days. This consisted of:
-starting the car at 7am cold on monday and tuesday
-sitting in traffic for 15 minutes on monday and tuesday
-spirited driving back home on monday and tuesday
-quick trip to walmart
-quick trip to the bank
-5 minute drive to my friends house

i filled up yesterday. i drove 184.5 miles it took 7.575 gallons. that's 24.4 mpg. that consisted of driving to work 30 miles, and back home another 30 miles from friday and saturday. it also includes driving to and from school on friday.


are you driving fast? are your tires properly inflated?
did you check for codes? are you making only 2 minute trips?
are you cold starting?

12 is still low no matter what. you should get a full 100-point inspection on the car from a good mechanic or a dealer

djipka

iTrader: (9)

after work post

So where do I start with the answers.

No gas smell other than the leak I had

Tire pressure is good (check it every couple of weeks and correct if needed)

When I swapped the ECU I tested it to see if it will show codes. So I know that it works.

I do drive hard sometimes. In the morning I let it run for e few minutes before I take off to school.

I aint been on the freeway for a while now ( and I miss the high speeds )

What scanner are we talking about? Where do I get such a thing?

Now with the noises. After the ECU swap I notices a whining type noise coming from the back. I mean somewhere around the fuel tank (just a general direction). I don't think its the pump because the noise is NOT there when the key is on but only when the car is running. It's that noise that I am concerned about. I think its something with the EVAP system which means that the canister could very well be involved.

What else?
I think that covers it all.

Trajiksmax

What was the reason why you changed the ECU? Definately an emissions problem. Could be that the ECU you have in it now is for a OBDI system. I believe some where between 95-96 Nissan changed to a OBDII system. Like you said check the evap system on the car Canister crack, loose or unconnected hoses, bad sylenoid valve, etc. I am leaning towards that the ECU is not communicating with your emissions system. Is it Cali or Fed spec?

KRRZ350

iTrader: (29)

Exactly. '95 fed specs didn't have an evap purge system. Next two things would be o2 sensors and dragging brakes

klemenz

sorry that was just sarcasm.

something is most definitely wrong with your car

djipka

iTrader: (9)

the car is fed spec so is the ECU.
the reason for the swap was because I found out why my CEL was constantly on and there were 2 codes that wouldn't erase. I came to find out that my cat had been stolen in the past and that's the reason for having a rebuilt title. The engine in it is from a 95 and that's why the CEL was on all the time. There were missing components on the EVAP system. I tried to get some of them and make it work but I got nowhere because I was missing some of those little valves that I couldn't find plus it was cheaper to swap the ECU.

ALL 4TH GENS ARE OBDII!!!!!!

brakes are fine.

I'll have to check the Canister one of these days. No time though until the holidays start.

time for church now. thank you all for the input so far!

FallenOne

iTrader: (17)

i knew it was sarcasm but im just making a point that even at high speeds. for long durations and frequent stops im still getting great gas mileage with a bad 02 sensor, so hes got something bigger. im thinking mabey his MAF is off... i know this sounds odd mabey im WAY off, but mabey he should put the car in Limp mode (disconnect the MAF) for a bit and see if he gets better mileage...

They do have the OBDI Consult in the fusebox if im not mistaken.

http://forums.maxima.org/avatars/pmo...ine=1202198098

djipka

iTrader: (9)

I have swapped the MAF too and have done the disconnect as well. I did that when I was testing the ECU.

On the 95 the OBDII connector is on the passenger side kick panel right by the ECU. The ECU itself is made for OBDII.

BTW I'm writing from church right now

djipka

iTrader: (9)

I was thinking today about this whole issue here and I have a question to ask.
Is it possible to plug up all the vacuum lines for the EVAP and canister and go without it? And if it is is that gonna affect my gas mileage?

fat_kid

iTrader: (13)

remove foot from gas pedal, instant increase in mpg

djipka

iTrader: (9)

it aint as easy as it sounds. that's why we have maximas anyway, right?
and what about my question above?

thegoldenmax

a bit off topic but where is the ecu i may have shorted mine out while trying to install a remote car starter. i hear theres a fuse on the ecu itself, or i may have just blown a relay not sure and im stumped plz help

ImmaSquashYou

iTrader: (7)

that is not off topic..that is thread jacking....anyways.

I'm not sure if you did this, didn't really read throughly of what you had done, to try to fix this problem but did you change the air filter? Did you replace spark plugs? If you did replace spark plugs, did you replace it with the correct ones from the dealership the NGK platinum that are like $22 each? did you clean your throttle body? meaning taking apart the intake tubing and cleaning the butterfly and the throttle body itself? Did you change your oil recently? For some reason, if i dont change my oil in the recommended time i see a drop in gas mileage. And try really hard not to rev over 2-2.5 rpm, that raises your gas mileage significantly. It also seems that you're driving a lot of local short distances, so keeping it below 2.5k won't be that hard as long as you don't have to pull out into high speed traffic.

djipka

iTrader: (9)

I can tell that you aint read a bit of what I have said
I have changed all of the filters, plugs and that with high quality and Nissan recommended once. TB, IACV and many other things have been cleaned as well. New belts, new O2 sensors and the list keeps going......
I am picky about my car and I only do the repairs when I can afford the quality parts.

P.S. I am trying to be a little easier on the gas pedal but its way hard for me
Also when I drive in town, that is up to 45 mph I always have the O/D off so that I get better mileage that way. Or may be that is a part of my problem? I look at this as it is a manual. I try to keep the rpm between 2000-3000 because that is the optimal range for many things such as cooling, economy etc.

92gxe/cg2

iTrader: (2)

Overdrive is 4th gear, why would u want that off for better mileage? If you leave overdrive on your car will shift into 4th gear under light acceleration at pretty low speeds (i think in my auto 3rd gen it was like 25) bringing the engine speed down therefore giving you better gas mileage, so you might want to start leave OD on. Although it can be said that when driving around town at low speeds with alot of stops its better to leave OD off to prevent the trans from "gear hunting" if your hitting 45 i see no problem in leaving it on. I never took it off and im sure most ppl on this site dont either.

ImmaSquashYou

iTrader: (7)

heh, yea, i read through some of your posts and thought i read that you replaced them, but when i went back to find it, i was like screw this, i'm not re-reading this whole thing.

Anyways, yes, definately keep our overdrive on. Meaning there should be no light on ur dash taht says o/d. When we mean scanner, i think the other orgers are saying to rent one from autozone. Its a sanner that hooks up underneath ur driver dash to test the codes. (i'm sure you know what i'm talking about and sorry if i'm talking to you like you do'nt know what your talking about). Since you did have an ecu swap, maybe it didn't fully reset for some reason. How long have you had your spark plugs in there? If its been a while, maybe pull them out and see if your running rich or lean by the color of your spark plugs. I really can't think of anything else that will give you such horrible gas mileage. Did you try throwing in one of those fuel injector and running 93 octane gas? And go to a good gas station, like a sunoco, mobil, lukoil, exxon. Exxon tends to give me the best gas mileage for the i30 for some reason. I know its not suppose to make a difference, but it does, and i can't complain. do you have an exhaust leak by any chance? Do you have any mods?

p.s., when i'm rolling at around 30-45 miles an hour, i'm usually at around 1.5-2k rpms...

internetautomar

iTrader: (30)

according to the FSM 4th gear does not engage until 70-75mph! (98 I30 FSM AT-284) GM cars engage at 45mph when not at WOT
this does explain my crappy mileage, I just about never hit 70.

t_ahan

well the only noise i think i read about was from the back but u said it might not be the pump cause it only does it when the car is running and not KOEO...i think the pump will only run for about seconds without seeing a crank signal before it shuts off ....i would try to pin point that whining noise jus to know where and what it is if every thing else has been checked over

allensteiner21

iTrader: (6)

consult is not obd1 - food for thought

92gxe/cg2

iTrader: (2)

Well I don't know about that, i mean OD is 4th gear and in my old max i could easily notice the 1-2, 2-3,and then 3-4 and the lowest i got it to engage in 4th was at 25 under very light acceleration. 70-75 makes no sense to me....

Either way OD will low engine speed and raise mileage is the main point, obviously.

djipka

iTrader: (9)

so many posts since I checked this last

The thing with the O/D. the reason why I leave it off is because when driving a BMW it shows you on the dash how much gas you are using and it appears that the car burns more at lower RPM (trying to accelerate in stop and go traffic). The reason for that would be that if you are in a higher gear and try to step on the car the gas is gonna go in the cylinders but it will not burn all the way and you still will be getting nowhere. I had a little mazda 323 back in the day and I put one of those Econ gages in it and that showed the same results as the BMW thing does.
Also with the O/D off I am constantly in a good RPM range to get response out of the car when I need it, meaning I save time from down-shifting and the tranny searching for a gear.
So far on this tank I have gone 60 miles and the little arrow just started going down. I think I could do 100 miles before I go down a 1/4 of the tank.

Interesting fact is that I have always gotten way good mileage on the freeway even at high speeds (80+ mph). I mean even when the car had bigger problems. right now i think its mostly the cold driving in the mornings and not letting the car warm up enough. there are times that the temp barely goes up to the middle before I pull into the school parking lot. I also am always late so I drive kinda hard quite often. I feel blessed to have a VQ under the hood because if it was some other car and different engine it would have been way beat up by now with the way I drive.

S1cTech

Are you sure you did your math right?

12mpg would mean you are getting like 170 on a full tank filled to about 14g. So I highly doubt that.

djipka

iTrader: (9)

Well I filled up all the way. what went in is what I had used that week. I always zero out the trip so that I can keep track of this stuff. So I take what the trip is showing and devide by the amount of gas that I filled up.
You can do the math if you want.
Trip=90 miles
gas put in=7.6 gallons.
90/7.6=11.84 .......
I put into consideration that there are long idling times as well. I hate to shut the car when I am around it or when I am not going to be at a place for very long.
I believe its cheaper to buy gas that to change Starter.

99BettySE

Not in the not-so-long run. Idling is THE biggest killer of gas mileage; think about it: when your engine is running it is using gas, and if you aren't moving, you are literally getting zero miles to the gallon.

Fuel injected cars only take as much gas to start them as they do to idle for 6-10 seconds. This is why hypermilers shut off their engines at red lights (those crazy people who get 50+ mpg out of a non-hybrid V6).

I could definitely imagine someone getting such low gas mileage just from long idling. Shut your engine off every once in a while and see how much of a difference it makes.

Also your starter is not going to burn out anytime soon just from shutting down when reasonable.

ImmaSquashYou

iTrader: (7)

agree with betty. If you are going to be in the store for more than 30 seconds, shut it off. Any most important of all, some 14 year old can hop into the driver seat and drive away. I cannot suppose tyou do THAT many trips into a store without having to be in it for less than 2 min. Not sure what you have in your car, but i used to keep my car running when i used to bump music in a parking lot with all my friends after i got off work. We would just hang out there for a little since we really had no where to go. That killed A LOT of gas, but i did'nt care cause gas back then was like $1.23 for super. you gave the guy a $20 and do a fill up and you'd get change back. I can understand the logic behind the o/d thing. But i personally think that you might burn the gas you've saved by going 45 mph without o/d on if you're cruising down the local road for like 5 min. Either way, in local driving, i get about 160-170 on a half tank, highway driving is around 200-220.

But again, are you using good gas? Do you fil up at BP a lot? BP here on the east coast is a killer for gas mileage. I would fill up with BP gas and only get around 14-16 miles a gallon. It seems that they put a lot of ethynol in the gas...