2001 Pathfinder LE with terrible gas mileage

[fzrr]

Noobie here. I've recently bought a used 2001 Pathfinder in Toronto with 180k on the clock and was expecting the gas mileage to sit around 14mpg. But after a couple tanks of gas and babying the throttle as much as possible I find i'm only getting 11.5mpg which seems a bit excessive.

What are some things to check to see if there is anything wrong with the vehicle? The previous owner said the MAF was just changed but didn't know if it was with a genuine or aftermarket part.

Is it worth ordering a new MAF sensor or are there other things to check first?

[Towncivilian]

Welcome to NICO!

I would start by running a 20oz bottle of Chevron Techron fuel system cleaner in a full tank of gas (preferably making only shorter city trips, not burning through the entire tank in one go like you would on a lengthy highway trip), then changing the fuel filter.

Also, adjust the accelerator and cruise wires (this probably has nothing to do with fuel economy, but is a wise idea regardless since slack has probably developed after 12 to 13 years of being on the road). See page FE-3 and page EL-258 of the factory service manual respectively for adjustment instructions.

Is your "service engine soon" light on? If not, does the "service engine soon" warning lamp illuminate with the ignition set to "ON"? Tires inflated to correct pressure as listed on the driver door jamb sticker? With 180k miles, the spark plugs were supposed to be replaced around 105k miles. Pull one and check its condition (post a photo if you're unsure of determining its condition) and make sure it's the specified plug (NGK PLFR5A-11).

Since you've just purchased this Pathfinder, make sure there are no outstanding recalls. Give your local dealership a call and provide your VIN number to them, they can run it and see. I would also suggest downloading a PDF copy of the owner's manual. What's the manufacturing date of your Pathfinder? I'll need this to link to the proper revision of the factory service manual as well, which is leaps and bounds better than the Chilton and Haynes manuals. I'd also suggest skimming through the general information thread as it contains a wealth of information relevant to maintenance of your Pathfinder.

[Slumpert]

If the knock sensor is bad, you won't have a "Check Engine Light" but you will get bad MPG.. Be sure to have someone check your ECU for codes when running.

[fzrr]

Thanks for the info so far. Can't find Chevron Techron cleaner up here in Canada so i'm going to try a couple tank fulls of Red Line SI-1 Complete Fuel System Cleaner then i'll change the fuel filter and see how it goes.

There is no engine lights coming on and the car seems to run perfectly fine but i'll try find an EFI place in Toronto and see if they can plug in a scan tool and see if there is any codes coming up.

After that I might try order a new MAF using the Maxima part number and see if there is any improvement.

[Towncivilian]

SI-1 is great, it has more PEA than Techron even. Let us know what happens.

[Buzzman]

Noobie here. I've recently bought a used 2001 Pathfinder in Toronto with 180k on the clock and was expecting the gas mileage to sit around 14mpg. But after a couple tanks of gas and babying the throttle as much as possible I find I'm only getting 11.5mpg which seems a bit excessive.

OK, so being Canadian as well, I first calculate my 'mileage' by using our system of litres/100kms.
From there I convert to both Canadian mpg's, and American mpg's.
So, two questions: What are you getting re: litres/100kms, and secondly, is the 11.5 mpg you are getting calculated using our gallons, or American gallons?
As a comparo, I get between 14-16L/100kms in the winter. I have an '02 Pathfinder.
Thanks.

[fzrr]

I also did the same and just googled litres/100km to mpg so not sure which gallon the website i clicked used.

But the last 2 tanks i got around 4.8km per litre which works out to 20.8L/100 all 2wd and really taking off slowly from lights etc.

[Buzzman]

But the last 2 tanks i got around 4.8km per litre which works out to 20.8L/100 all 2wd and really taking off slowly from lights etc.

That's definitely bad.
Even on my worst cold days, letting it sit while idling to warm up, running AWD in the snow, in the city, I still got better mileage than that. Ouch.
OK, so to start I would check/replace the obvious first. Stuff like air and fuel filter for example.
Do you have any maintenance history on this truck?
How old are the plugs? If you're not sure, you may want to get them replaced. Etc. etc.
Keep us up to date.
Cheers.

[pdxdan]

For what it' worth I just bought a 2001 Pathfinder down in Australia. It' a 3.8 gas automatic and it is only getting 16.6 liters per 100k which comes out to 14 mpg measured on a trip driving at 90-115 kph. The offical numbers should be 10 liters per 100k on the highway but there are a lot of other factors that infuence fue economy besides powertrain.

My Pahtfinderhas a bull bar, UHF radio antenna, roof rack, mudguards, and all terrain ties which all hurt fuel economy due to aerodynamic drag a rollin resistance.

I'm still looking to see what I can on the fuel economy side since gas down here is currently $ 1.60 AU per liter.

The Pathfnder has 235,000 kilometers or 146,000 miles on it. Is there a sequence of things to check in the order of cost?

[Buzzman]

For what it' worth I just bought a 2001 Pathfinder down in Australia. It' a 3.8 gas automatic

Whaaa? You guys get a 3.8?

[fzrr]

Quick update. After running 2 tanks of Redline fuel system cleaner there has been a very slight improvement in gas mileage. Last 2 tanks I got 18L per 100 and 19L per 100 respectively. Replaced the fuel filter today so will see what happens on the next tank...I'm not expecting miracles though.

Next up will be trying to find a shop to check ECU codes I think.

[fzrr]

Welcome to NICO!


Is your "service engine soon" light on? If not, does the "service engine soon" warning lamp illuminate with the ignition set to "ON"? Tires inflated to correct pressure as listed on the driver door jamb sticker? With 180k miles, the spark plugs were supposed to be replaced around 105k miles. Pull one and check its condition (post a photo if you're unsure of determining its condition) and make sure it's the specified plug (NGK PLFR5A-11).
.

The service engine soon light is not on but I just checked and with the ignition set to ON it is illuminated. What does this indicate?

[Towncivilian]

It just indicates that the bulb is working.

Were spark plugs replaced if due?

[fzrr]

Haven't touched the spark plugs yet. I've only just moved to Canada from Australia so I'm without tools to pull the spark plugs and check the color. I'm at the mercy of getting to mechanics on Saturday mornings when i'm not working.

[fzrr]

Well what do you know...first tank I've run through after the fuel filter change and I got 14mpg! Big improvement from what it was getting previously. Hopefully this has solved it or maybe its the warmer weather now?