WHY do I get 12MPG?????

[djipka]

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]

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]

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]

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]

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]

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]

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]

what about my friend than?

[Maxgig]

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]

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]

Originally Posted by 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

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]

Originally Posted by FallenOne

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

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

[J RO 9]

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]

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]

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

[klemenz]

Originally Posted by FallenOne

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

sorry that was just sarcasm.

something is most definitely wrong with your car

[djipka]

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]

Originally Posted by klemenz

sorry that was just sarcasm.

something is most definitely wrong with your car

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...

Originally Posted by djipka

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

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

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

[djipka]

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]

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]

remove foot from gas pedal, instant increase in mpg

[djipka]

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]

Originally Posted by thegoldenmax