My 2001 Pathfinder's gas mileage has dropped by over 10% in the past couple of months. It has 100k kilometers. Besides regular oil changes, I've changed the air filter, and thats about it. The check engine light came on once recently after it ran rough for a minute after startup. I had it reset after the garage couldn't find a definite problem. They said it may be the coils or an oxygen sensor, but if it was the light will come back on.

That was a month ago and I still get poor mileage but the check engine light hasn't come on. I don't want to replace a bunch of parts that don't need replacing Any suggestions?

Sounds like you are at the same place I was with my 02 pathfinder.I first started getting check engine lights at around 100k Kms. as well.After reading other threads here, I've learned that 02 sensor failures are a common problem starting at 100k Kms. I've replaced both back sensors and have no more engine lights. The upper sensors seem to be OK.I've also come to the conclusion after reading other posts that you are probably better off getting the sensors at the dealer, as opposed to a parts store.I'm now at 160k Kms., and my truck runs great. Good luck.

So when did a Pathfinder/QX4 'ever' get good mileage...

Rating my 2001 QX4 gets 10's ....except for gas mileage...

Jack1944 wrote:So when did a Pathfinder/QX4 'ever' get good mileage...

Rating my 2001 QX4 gets 10's ....except for gas mileage...

true, true. . I got 13.5 on my last half a tank. ... all in-town, careful driving. (but by comparison, my 240sx will typically get 19)I figured the fuel cost wasn't tooooo bad to adjust to.

yea.. lately ive been getting 13.5 - 15.5 mpg

Does anyone have any idea why my Pathfinder millage has dropped around 10% when the engine light hasn't even come on? If it was an oxygen sensor or something similar, then the light will indicate a problem. I know that Pathfinders don't get great millage, but if it drops by 10-15% wouldn't that indicate a problem.

I've checked all the usual things, tire pressure, air filter, oil, and everything seems ok. Any suggestions would be appreciated.

i tried etahnol and so far a get about 10-12% better fuel consumptionon my 01 pathfinder.I normaly use 91 octane grade

A BUMP WITH A POSSIBLE EXPLANATION.

A possible culprit to poor fuel economy can be the Mass Air-Flow Sensor.

Component Description

The mass air flow sensor is placed in the stream of intake air. Itmeasures the intake flow rate by measuring a part of the entireintake flow. It consists of a hot wire that is supplied with electriccurrent from the ECM. The temperature of the hot wire is controlledby the ECM a certain amount. The heat generated by the hot wireis reduced as the intake air flows around it. The more air, thegreater the heat loss.Therefore, the ECM must supply more electric current to maintainthe temperature of the hot wire as air flow increases. The ECMdetects the air flow by means of this current change.This is how the computer regulates fuel usage.

SOURCE: NISSAN XTERRA FACTORY MANUAL

If the wire is dirty, has a peice of fluff on it or it's oily the computer has to push more voltage through the wire to maintain a constant temp. This equates to higher resistance. Which can directly affect fuel economy. Basically by having the dirty MAFS the computer can be fooled into thinking you at highway speeds when you're in fact puttering around town. So you end up wasting fuel.

The wire resides inside the sensor body(look inside the red circle on my image)

The fix is simple.

Unplug the MAF Sensor.Remove the 2 screws used to hold the sensor in place.

(Do this part away from the engine and your paint job)Spray ONLY electrical contact cleaner at the sensor's wire and let it air dry.

Do not touch the wire with anything as it can be easily damaged. ( A new one is not cheap either!).

I just did mine a week ago today and it took 10 minutes. Easy fix you can do yourself!

And to add to this fix I was getting around 350 KM (just over 200 miles ) to a tank on my Xterra before I did this.

O2 sensors were fine but the MAFS was dirty. After the clean up I am on-track to get just over 500km. ( just over 300 miles)

will that work with the vq35 engine in the pathfinder because ive had the same problem with thecar since i bought it very poor gas mileage. on another note can i swap the stock 05 g35 injectors in to my 2001 pathfinder Le in hopes of getting better acceleration

Try the MAF cleaning first, but most probably O2 sensor I would think.You might not have a SES light because the sensor may still be within the limits the computer has before showing it, i.e. the sensor is on the way out but is still sending an albeit weak signal, either that or it is sending an incorrect signal. The computer just sees that it is receiving a signal within the set range and everything is okay, even though in reality it needs changing.A word of warning when cleaning the MAF: disconnect your battery and leav for at least a few hours to make sure that there is no energy in the circuit. I mistakenly disconnected the harness from the MAF when the engine was running, and that f****d it up completely!! And that was a thousand dollar fix from the dealers!!!!!! (here in Mexico)

Essentially the MAFS sensor is located close to and fastened in the same manner as the Xterra's. At the very least it will be located somewhere between the airbox and the plennum's aluminum intake throat. (PS: A good rule of thumb is to disconnect the negative terminal on the battery before doing ANY sensor work. ) And if you think you can use brake cleaner instead of electrical contact cleaner....my advice is don't. They are not the same product despite what some people may believe.

To answer the injector question: As far as I know the injectors are not compatable between the 2 platforms. BUT this is the info I have and not a documented fact I am 100% sure on. Perhaps our Nissan Tech can enlighten us.

I read somewhere that aftermarket air filters may cause a problem with the MAF. They have silicone in them, it is then deposited on the MAF. I bought a can of MAF cleaner. 2 torx bolts, DISCONNECT POWER SUPPLY. Spray the he11 out of it, let dry. VROOOOOOOM. Huge increase in power. Cheap and simple, you should notice a difference. I am using the dealer filters to be safe, or until someone can verify/deny the aftermarket filter problem. Thanks for all the help. saved me A TON OF $$$$$$.

I think what you might be reffering to is the K&N filters that have to be oiled after cleaning them. If you over oil them, then you can definately damage the MAF sensor. It's a good idea to leave the filter out for a few hours before reinstalling it, just to let some of the oil evaporate. On another note, I've never heard of a specific cleaner for MAF sensors. Someone in an earlier post suggested using contact cleaner. I haven't tried it yet, but was going to try it when the weather got a little better. Also, how much does it cost? (MAF cleaner, I mean).P.S. My Pathy is in the shop for e-testing. I need another O2 sensor (engine light is on again), plus I'm having new plugs installed. I was going to do that myself, but everyone I talked to said it's a pain in the butt. It's costing 2 hours labour plus the plugs. Am I getting ripped, or is 2 hours normal?.

Wasn't sure if I should mention the brand . I heard the Fram brand in particular uses silicone in the manufacture process and this is what "clogs" the sensor for lack of a better term. The filters I use are single use ones. I did see a huge difference in the one I got from the dealer. The orange frame on the Frame seemed rubbery to me. The MAF cleaner I got was overpriced at 5.99 a can. It is made by CRC. wwwcrcindusrties.comI was told not to use brake cleaner. Be very gentle with the MAF sensor its about $400 to get a new one.I judge my repairs by the book time .5 to 1.0 USUALLY means easy to get to. However, I took mine in for the oil cooler o-ring and oil pressure switch. $140. seemed cheap when I tried to get a wrench on the bolt . No way to get at it. I've read that many people have changed their own coils. I have to change #6 when it comes in. Plugs, I'm not sure. All it takes is one plug to be a pain in the ... to offset the cost. I would look and see how much stuff you have to take out of the way to get at them.GlDan

At least fram doesnt have oil in the filter, thats what really gunks up a MAF sensor. I'm sure the silicon is at a minimum, if any. Some good info in here.

Hey, just got my truck back from e-testing and stuff. (had it done at the dealer by the way). I asked for the old parts back and checked the old O2 sensor. It was a Bosch, in case anyone was wondering. Not sure if it means anything, but it looked pretty bad. The old plugs however were in pretty good shape considering I have 165K Kms on it. They were the originals. I'm glad I had them do it. It's not a fun job. It passed the e-test with flying colours. Service advisor said it was one of the cleanest running test results he's ever seen. Now I have to go to the license bureau and renew my plates and driver's license. More money for the politicians.The truck also felt better when I drove it home. Ran really smoothly.I'll keep an eye on my gas consumption for a while, just to see if it gets better.