[pathydaddy]

so i go to the gas station and fill up i even top it off to where gas spits back out then i jump in the pathy and reset the trip meter.its a 95 auto with the stock 31 10.50 15s and a 21 gal tank yet litterally all straight freeway at 65 and 70 miles down the road and ive already burned up a half tank per what my gas gauge says. so i pull in the the gas station and fill it back up and sure enough takes a good 10 plus gallons i have looked for leaks i have looked for un plugged sensors and i have even thrown the scanner on it just for the hell of it even tho the CEL isnt on so please SOMEONE give me some ideas to look at here!!!


are there known locations in the fuel lines to crack?
what could casue this?
am i overlooking a huge problem here?

[Tungsten]

mass air flow sensor
coolant temp sensor
wheel alignment
fan clutch
catalytic converter
air filter
spark plugs
egr valve

[pathydaddy]

but wouldnt a few of those throw a CEL?

[adamzan]

The maf and EGR will I know for sure, it did on mine. But that is some horrible mileage. Maybe your cat is clogged up? How old is your 02 sensor? Did you check to see if one of your brakes are dragging, that would definitley bring the mileage down.

[BowTied]

Was this sudden or getting worse over time?

What does your temp gauge show? If it stays low even after a while, the stat may be stuck open. This means the truck would take a long time to warm up and use way more gas.

Original O2 sensors? They could need replacing...

There are lots possibilities here. Can you give more info?

This post has been edited by BowTied: 17 October 2009 - 03:50 PM

[pathydaddy]

BowTied, on Oct 17 2009, 04:50 PM, said:

Was this sudden or getting worse over time?

What does your temp gauge show? If it stays low even after a while, the stat may be stuck open. This means the truck would take a long time to warm up and use way more gas.

Original O2 sensors? They could need replacing...

There are lots possibilities here. Can you give more info?

im not to sure about any of the rig... i have only had it for 3 weeks... and already had to put in a new auto tranny... the rig has an abundance of power i dont think the breaks are dragging cat could be plugged up a bit can someone give me a list of cheap to expensive to try and figure it out....

[Precise1]

Ok, it's a 95, but put that in your visible information please. It helps everyone...

Did you say you got 7 MPG??

I almost passed this by as you said you have thrown a scanner on it so I thought it must be 96 and never. On yours, you can read the ECU for faults, the directions are in the 'How To' section.

Did you say you got 7 MPG?? I have never heard of that bad milage. Have you tested the O2? There is a thread about what values it should have.

B

[pathydaddy]

the auto shop i took it too said they scanned it and no codes came up but after reading this a few more sites aparently you cant scann it due to not being OBD2.. they tried to take me for a ride lolbut its not working casue im not that retarded lol im not new to cars and how things work just new to nissans.. so i yea lol ill try learing the fault codes thread and see what i can make of it any more info would be great!!!

[MikeV]

isn't it a 16 gallon tank? that would throw the math off but still is bad on gas...

[GrimGreg]

pathydaddy, on 18 October 2009 - 02:37 AM, said:

the auto shop i took it too said they scanned it and no codes came up but after reading this a few more sites aparently you cant scann it due to not being OBD2.. they tried to take me for a ride lolbut its not working casue im not that retarded lol im not new to cars and how things work just new to nissans.. so i yea lol ill try learing the fault codes thread and see what i can make of it any more info would be great!!!

Actually you can use an external reader on it to check the codes too. There are some scanners (high end shop types) that can preform certain test modes on your system. My step-dad has a MODIS from Snap-On, it had a MAF and O2 sensor test modes, basically it just reads the signals from the sensors to see that the proper signals are being sent.

[Kingman]

MikeV, on 19 October 2009 - 08:37 AM, said:

isn't it a 16 gallon tank? that would throw the math off but still is bad on gas...

21 gallon.

[carwilef7]

It would help if we knew the exact mileage from fill-up to fill-up. I regularly put in 9 or 10 gallons when it shows half a tank, but I've usually gone 140-150 miles or more in city driving.

That said, (and mine is a 97) the first week I had it, it got like 11 mpg because I was trying to figure out why it started running like crap and stalling after two days - turned out to be a cracked intake boot and a bad MAF sensor - no codes or CEL either, at first. I spent more time than I thought letting it idle while I was scratching my head.

Later on, I found a bad coolant temp sensor - pretty much by serendipitous means - and it never set a code for THAT either.

Fuel gauge is weird - 35 miles to get to the F, then 3/4 at 75, 100 miles puts me at about 5/8. I've filled up at E and only put in 16 gallons. All of this working out at about 15 mpg, give or take. 21 gallon tank.

[pathydaddy]

so had the values checked on the O2 sensor and checked out fine maf sensor is good no issues with the egr valve so my mechanic is wondering if on a pathfinder in 60 degree weather the temp gauge goes up like less than a quarter inch and engine isnt running very warm hes curious if thats telling the ecm to run rich thus loosing gas mileage and also the fact that at idle of 4k rpms very minimal pressure coming out the tail pipe hes thinking plugged cats? what yall think on these ideas oh yea the rig has 180k on it no oil burning has abundance of power too.... yet still about 10 mpg with freeway driving

[MY1PATH]

1)unbolt the cat and look thru it with a BRIGHT light on the other side. if u can't see its cloged. If you get a magnaflow direct replacement you won't need such a bright light (breathes better)
2) sensor values may be correct but are they clean? an o2 sensor with deposits blocking it from may cause you to run richer.
3)Is there a chance your ECU may have "learned" a bad conditon in the past and when something was fixed the ecu never reset? If so maybe resetting the ecu may help. If so, unplug the battery for a few hours, stomp the brakes with the ign on to complete the reset(elctronic drain so it "forgets" old habbits) b4 putting the battery back on. Then take it for a drive and let it re-map all the fuel curves.
If I'm wrong on the third one; trying it didn't cost you anything but time.

This post has been edited by MY1PATH: 07 November 2009 - 01:37 AM

[Precise1]

There was a recent thread on the temp sensor for the ECU which can indeed mislead the ECU significantly. Let me try to find it, Terrano1992 gave the meter readings for diagnosis.

B