Hello.. been trying too figure out what forum too join, as i was just [ given] a 1999 pathfinder with 139,000 miles...SO here i am..... I currently can get only about 230 miles out of a tank of gas, which i think is BAD !!!!! As for not ever owning a nissan [but is a 23 year crysler tech] - I thought maybe just a simple tune up.. After a more thu check i see what looks like nothing ever has been done too this veh. - So i did a complete tune, also a decarb of combustion and intake, check MAF Sensor with volt meter [ok], new fuel filter, new temp sensor for ecm, right bank upstream 02, which took a crap after two fuel tank fills with fuel cleaner..- I saw alot of people on net complain of drop in fuel mil, but no possative answer that may be my issue..I wanted too look at fuel trim on a scaner but where i work they dont have one, that works on this veh.. So does anyone have any thoughts????? maybe the left upper 02 ??? Hate guessing and changing parts...Wish i had scaner..... Was told nissan this year has a wide range in ecm before it will set 02 code... Not sure if thats tru tho. Any insight would be great..

If you are saying you are getting right at 11mpg (230miles divided by 21 gal) then yes, it sounds like you have an issue somewhere. But the ball park for an automatic is 15-19 and a manual is 18-20. Most people get a little better than that. As for a fuel mapping test it won't help unless there is a way to adjust it...I don't know if it is or not (adjustable)

Check the vacuum hose to the fuel pressure regulator at the back of the engine; sometimes these will fall off or split, causing the fuel pressure to run at full pump pressure. Wouldn't hurt to check the fuel pressure, if you have the equipment. Saying how many miles you got out of your tank, to me, is not an accurate measurement of fuel mileage. A better method would be to log your mileage and record the actual number of gallons of gas you install in the tank at fillups. The larger the sample, the more accurate the results. Pathfinders with VG engines were never known to be particularly good on gas mileage nor be very big in power, however the are a durable engine. Since you say that nothing was ever done to it, you have to be concerned about the timing belt, which should be replaced every 105,000 miles or 6 years, whichever comes first. The engine is an interferance type engine.

UGGGHHH, Its a interf eng ? Was told it wasnt. mmmmmmmmmm.......Thanks for more info too check.... I went ahead and did the left upper 02 sensor today. Plan on doing lower as soon as i can... I see they put bosch 02 orig in this at new.. NO WAY ill put a bosch 02 sensor in any veh, been burnt on them too many times here with veh's .. [ THINK THEY HAVE A POOR QUALITY CONTROL now] as bosch use too be good.. Im putting in DENSO as they been good too me and tech's here.

Just checked fuel reg hose.. Seems too be fine.. Only got it off at intake end, and there is vacuum and rpm increase, and when i put it back on rpm back too normal.. sooooo im figuing its not leaking..- couldnt get my hands back there too take it off at regulator tho....- Feels fine and here no leak..- So what is easiest way too check fuel pressure on this ? is there a port on the fuel rail too check it. ??? i couldnt see one. I do see that on pressure line where it bolts too fuel rail, it looks like it might take a tool too check pressure that early chrysler 3.0 L use too use..... if so i may have it still at work... ------- Any idea on what pressure should be running or not running.. ?

YUK ENG NOISE NOW.. Nope, just something else gone. -- Bad harmonic balancer. Should off kept my jeep.. This veh is eating up all my cash..

One thing after another... guess its what i get for veh never have any service besides oil change.. Any info on fuel pressure check or spec guys

The fuel filter is located under the vehicle, above the rear axle. This is the easiest place to install a fuel pressure tester, as the filter is attached to rubber fuel hoses. Pressure should be around 34-36 psi regulated and they are usually 42 psi or higher unregulated.

There has always been some question on the 3.3L as to whether it is interferance or not, largely because the engine used in the Mercury Villager (the Quest's sister) and the Quest were made to be non-interferance. There have been a number of cases where 3.3L VG's have experieced broken timing belts in the trucks and have not experienced valve damage, but it is still an interferance type engine and the potential for bent valves is possible.

As far as engine noise, what type? Tapping or ticking are common noises, usually resulting from cracked exhaust manifolds (right bank) and sometimes bad hydraulic lifter(s). Exhaust shield rattle is also common.

Thanks for fuel pressure specs.... And on that noise. It sounded likd lower end knock. But its a bad harmonic balancer.. Its ready too fly apart.. One thing after another....Should of kept my jeep.. Sory.

My tip, change out the fuel filter when the tank is on E. less mess with gas spray/leaking.

brht27 wrote:My tip, change out the fuel filter when the tank is on E. less mess with gas spray/leaking.

Another thing you can do is de-pressurize the system, first. Pull the fuel pump fuse and start the vehicle; run it until it stalls then crank the engine a few seconds.

Already did a major tune up. Including the fuel filter guys.... Did a 24 hour battery disconn,[between yesturday and now.] - too see if maybe my parts i have changed has fixed gas miledge, thinking maybe ECM might have old values stuck in it and ecm using bad info ??. Worth a try i guess.