High Fuel Consumption

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ice4x4
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Location: NZ

High Fuel Consumption

Postby ice4x4 » Sun Jun 09, 2019 7:15 pm

Hi,

I have bought a 2008 Pathfinder and the fuel consumption is very bad. I’m doing mostly highway miles with a bit of town driving and only getting 19 litres/100km. Information I’ve found says combined mileage should be 13.7l/100km.
Anybody got any ideas what could cause this excessive fuel consumption?


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palmerwmd
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Postby palmerwmd » Sun Jun 09, 2019 10:44 pm

Welcome to the path!!! :D

(which engine do u have)
With an older vehicle u can have several causes.
...many have done the following to improve fuel economy ( and power) in older vehicles
Most of these apply to the petrol motors (I dont know much about the Diesels)

- putting a couple bottles of injector cleaner detergent in the tank and then running the car fast and hard for as long as local laws let you get away with ( for cleaning injectors)
- Throttle body cleaning
- MAF replacement or cleaning (be careful if cleaning it yourself)
- Installing New sparkplugs

Those are some of the methods folks use to "freshen up" a motor to restore power and/or fuel economy.
I am sure I have missed some.

ice4x4
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Location: NZ

Postby ice4x4 » Mon Jun 10, 2019 12:31 am

Yeah it’s the 4.0l V6
There plenty power there it’s just using way too much fuel
Thanks for those tips

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smj999smj
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Postby smj999smj » Mon Jun 10, 2019 1:27 am

With the sensitivity of the electronic throttle, going easy on the pedal and keeping it steady while using the cruise control as much as possible helps a lot when it comes to gas mileage. You might also consider replacing the upstream oxygen sensors (stick with NTK or Denso brand) as they can get a little inefficient at times. Stock, I think 17 MPG tends to be the average combined mileage if it's 4WD. Cruising on the highway on a long, relatively flat, run and you might see 21-22 MPG. City driving and figure around 16 MPG. I never noticed any difference in mileage whether I was using 87 octane or 93 octane.

ice4x4
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Location: NZ

Postby ice4x4 » Tue Jun 11, 2019 4:47 pm

Yeah i have been driving very softly on the pedal and using cruise control as much as I can. If im only getting 19l/100km thats only 12.3mpg.

So something is not right...

ssobol
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Postby ssobol » Tue Jun 11, 2019 7:33 pm

ice4x4 wrote:Yeah i have been driving very softly on the pedal and using cruise control as much as I can. If im only getting 19l/100km thats only 12.3mpg.

So something is not right...
That's exactly what my '08 4.0 4WD gets with normal driving around my smallish town (50+% towing 4500#) using 87 octane gas. The EPA sticker said 14 mpg City and those ratings are usually optimistic.

I have not done any unladen highway driving to see if it improves.

I got the Pathfinder mostly for towing, so if it tows at 12-13 mpg, I'll be happy.

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underworld1001
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Postby underworld1001 » Tue Jun 11, 2019 10:37 pm

You can try changing the plugs if they haven't been changed already. I replaced mine and mileage improved a decent amount. Cleaned the air filter, use correct oil weight, make sure fan clutch isn't sticking. There's a few things that could be checked that would make a difference.

ice4x4
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Postby ice4x4 » Tue Jun 11, 2019 11:57 pm

Thanks for the tips,

I bought some new spark plugs today along with some injector cleaner, MAF sensor cleaner and throttle body cleaner. Will give those a go and see how I get on.
I did notice in the service record the spark plug service was missed, the car has 190000km's on it so if they are the original plugs then they are way overdue.

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palmerwmd
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Postby palmerwmd » Wed Jun 12, 2019 8:22 am

ice4x4 wrote:Thanks for the tips,

I bought some new spark plugs today along with some injector cleaner, MAF sensor cleaner and throttle body cleaner. Will give those a go and see how I get on.
I did notice in the service record the spark plug service was missed, the car has 190000km's on it so if they are the original plugs then they are way overdue.
be very careful when cleaning the MAF.
Its an expensive part

TooTallMike
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Postby TooTallMike » Sat Jun 15, 2019 12:08 am

Up stream O2 sensors can be the culprit. Mine was getting 17mpg easily and then it dropped to 13mpg. Connected my obd 2 and used torque lite and saw one of my upstream sensors had voltage way outside its normal zone so it was reading lean and was dumping fuel to compensate for the false reading. Replaced it through Rock Auto and it's been good to go ever since. Also your plugs should make a difference since they skipped the last go around. Good luck and I hope you get it fixed!

Also DO NOT TOUCH YOUR TB UNLESS YOU SEE ITS OBVIOUSLY CAKED UP.

I looked at mine wrong and had to go to the stealership to do the idle relearn after failed pedal dances. 120$

ssobol
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Postby ssobol » Sat Jun 15, 2019 9:55 am

TooTallMike wrote:Up stream O2 sensors can be the culprit. Mine was getting 17mpg easily and then it dropped to 13mpg. Connected my obd 2 and used torque lite and saw one of my upstream sensors had voltage way outside its normal zone so it was reading lean and was dumping fuel to compensate for the false reading. Replaced it through Rock Auto and it's been good to go ever since. Also your plugs should make a difference since they skipped the last go around. Good luck and I hope you get it fixed!

...
The upstream O2 sensors are referred to as A/F Sensor 1 in the Pathfinder Service manual, correct?

TooTallMike
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Postby TooTallMike » Sat Jun 15, 2019 11:52 am

...[/quote]

The upstream O2 sensors are referred to as A/F Sensor 1 in the Pathfinder Service manual, correct?[/quote]

No it's referred as "oxygen sensor 2" if you look under Engine Mechanical page 22 it mentions it.

I can find the rock auto part number of you'd like?

ssobol
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Postby ssobol » Sat Jun 15, 2019 3:09 pm

As I read the manual for the 4L engine, the A/F sensor is upstream and the O2 sensor is downstream.

The A/F sensor is changed via access behind the wheel well liners and the O2 sensors are on the exhaust tubes underneath.

From my service manual.
MIXTURE RATIO FEEDBACK CONTROL (CLOSED LOOP CONTROL)
The mixture ratio feedback system provides the best air-fuel mixture ratio for driveability and emission control. The three way catalyst (manifold) can then better reduce CO, HC and NOx emissions. This system uses air
fuel ratio (A/F) sensor 1 in the exhaust manifold to monitor whether the engine operation is rich or lean. The ECM adjusts the injection pulse width according to the sensor voltage signal. For more information about air
fuel ratio (A/F) sensor 1, refer to EC-142. This maintains the mixture ratio within the range of stoichiometric (ideal air-fuel mixture).
This stage is referred to as the closed loop control condition.
Heated oxygen sensor 2 is located downstream of the three way catalyst (manifold). Even if the switching characteristics of air fuel ratio (A/F) sensor 1 shift, the air-fuel ratio is controlled to stoichiometric by the signal
from heated oxygen sensor 2.
Since Courtesy Nissan lists the sensors at over $200 ea. I just want to make sure I'm getting the right part.

I did this recently on a Toyota van I have, the part was $197, but there is only one of them.

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smj999smj
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Postby smj999smj » Sat Jun 15, 2019 3:11 pm

ssobol wrote:As I read the manual for the 4L engine, the A/F sensor is upstream and the O2 sensor is downstream.

The A/F sensor is changed via access behind the wheel well liners and the O2 sensors are on the exhaust tubes underneath.

From my service manual.
MIXTURE RATIO FEEDBACK CONTROL (CLOSED LOOP CONTROL)
The mixture ratio feedback system provides the best air-fuel mixture ratio for driveability and emission control. The three way catalyst (manifold) can then better reduce CO, HC and NOx emissions. This system uses air
fuel ratio (A/F) sensor 1 in the exhaust manifold to monitor whether the engine operation is rich or lean. The ECM adjusts the injection pulse width according to the sensor voltage signal. For more information about air
fuel ratio (A/F) sensor 1, refer to EC-142. This maintains the mixture ratio within the range of stoichiometric (ideal air-fuel mixture).
This stage is referred to as the closed loop control condition.
Heated oxygen sensor 2 is located downstream of the three way catalyst (manifold). Even if the switching characteristics of air fuel ratio (A/F) sensor 1 shift, the air-fuel ratio is controlled to stoichiometric by the signal
from heated oxygen sensor 2.
Since Courtesy Nissan lists the sensors at over $200 ea. I just want to make sure I'm getting the right part.

I did this recently on a Toyota van I have, the part was $197, but there is only one of them.
The OEM sensors for Nissan are made by NTK and you can get them a lot cheaper at Rockauto.com compared to the dealer part.

BullDozer
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Postby BullDozer » Tue Jun 18, 2019 10:59 am

Don’t forget tires and brakes. Etc.
Fyi. I average 16.0 mpg according to mine. Thats with mostly highway. City only, I average around 12 Mpg


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