Hi,

I have a nissan bluebird SR20DE and I'm having problems with excessive fuel consumption. I'm getting 300km off 45L or 6.5km/L and I'm not driving it over 2500-3000 revs. It seems as if the choke is always on, as it nearly always idles around 1500 rpm until it finally warms up after about 15 minutes and it always smells of unburnt petrol out the exhaust. When I do give it a good squirt, a whole heap of black smoke comes out the exhaust.

Also I'm finding when I put it into neutral or put the clutch in and brake, the revs drop off to a stall and then they rise again.

Does anyone have a solution to these problems?

Cheers,
Chris

Kinda sounds like you got an injector o-ring leaking

I looked under the car and found the O2 sensor was all dented up, so I probed it and hooked it up to an oscilloscope and I also connected a scan tool to the ECU port. Both tools showed the the O2 sensor was constantly putting out a 10mv signal (even when it was warm), which says the engine is running too lean so the engine puts more fuel in to compensate. Also I hooked up an AVL DiX emission tester to the exhaust and this is what it compared to the manufactures specs:

Manufacturer specs:
CO2: 14.5-16%
O2: 0.1-0.5%
HC: 100ppm
CO: 0.3%

Current O2 sensor in car:
CO2: 11.9%
O2: 2.62%
HC: 294ppm
CO: 1.58%

Borrowed operational O2 sensor:
CO2: 12.2%
O2: 2.95%
HC: 234ppm
CO: 0.83%

Even with A working O2 sensor the stats are too high compared to the specs for it, but the Catilytic converter and it's sensor has been removed, which could be the cause of this. For your solution of the leaking injector o-ring, if that was the case wouldn't there be a lot of smoke on start-up and it be hard to start, from the leakage that would occur while the engine is stopped?

Fuel only dribbles out of the injecotr o ring when the fuel pump pressurises the rail, the momentary amount of fuel dribbled in after priming the fuel pump before starting the car is not enough to make it hard to start, especially since it is usually on one injector only. Other 3 cylinders start normally ;)

To confirm, disconnect the distributor wiring plug, pull out the spark plug leads and pull out the spark plugs. Try to start the car and watch the cylinder that has unburnt fuel pushed out of the spark plug tube in a fine vapour mist ;) Thats the cylinder that has the leaking injector :D

Hey I tried this the other week and no fuel vapour came out any of the cylanders when I cranked the engine over

I have a bad mileage prob as well on my SR20VET, getting similar (6.2 km/l) Xtrail, ez no/low boost driving h'way/city. Good tyre press. RON 95 fuel, no ecu codes.

I have a Blazt.biz OBDII/Nissan ConsultII system. I can see the O2 voltage oscillating rich/lean which I believe is normal, my idle seems a bit wide from 750 to 825 compared to my wingroad which is smooth between 750 and 760. I have data logging capability on the sensor output. Idle produces water in the exhaust.

Can anyone advise me on what to look for to improve the mileage based on this? What is the necessary plugs/gap, fuel filter, air filter procedure as well thx!

I have a bad mileage prob as well on my SR20VET, getting similar (6.2 km/l) Xtrail, ez no/low boost driving h'way/city. Good tyre press. RON 95 fuel, no ecu codes.

I have a Blazt.biz OBDII/Nissan ConsultII system. I can see the O2 voltage oscillating rich/lean which I believe is normal, my idle seems a bit wide from 750 to 825 compared to my wingroad which is smooth between 750 and 760. I have data logging capability on the sensor output. Idle produces water in the exhaust.

Can anyone advise me on what to look for to improve the mileage based on this? What is the necessary plugs/gap, fuel filter, air filter procedure as well thx!

Replace the O2 sensor ;)

Is the O2 not working? It swings rich/lean a couple times a sec. I believe that is normal.

How is a narrow band supposed to work?

It will switch between rich and lean but the O2 sensor in the VET is easily contaminated with soot and other pollutants, so the O2 sensor tries to maintain a closed loop signal and adds extra fuel. O2 sensor is only really supposed to last around 60,000km's(about 38000 miles)

Just because the voltage is varying does not meean the O2 sensor is in good condition :)

For example, if the O2 sensor is telling the ECU that AFR's in the exhaust are 14.7:1 but because of contamination, it is actually 12:1, then your using around 10% more fuel.
Getting 350km from a tank of fuel is not normal for the VET and the O2 sensor is the most likely culprit.

The other problem may be that you have a small boost leak between the turbo outlet pipe and the throttlebody, which will cause the engine to use more fuel as well.

Hmm, I guess I can take out the O2 and verify it using a propane torch. Loss of air after the maf can cause overfueling as well.

Just as a reference, what should the SR20VET mileage in an Xtrail hover around....easy driving? I am at 16L per 100Km atm.

thx

It will switch between rich and lean but the O2 sensor in the VET is easily contaminated with soot and other pollutants, so the O2 sensor tries to maintain a closed loop signal and adds extra fuel. O2 sensor is only really supposed to last around 60,000km's(about 38000 miles)...


I have found that replacement of the front O2 sensor on my first B13 smoothed out a lot of issues (no rear O2) and the OEM unit I took out was burnt, sooty,and looked every bit 125k miles it probably had been in service.

My first B13 had been running so rich it pooled unburnt fuel (cat was gutted due to the ceramic breaking up) and between 1-2 and 2-3 shifts I'd see 6" flames shooting out the tailpipe a la F&F. There was a good amount of power loss up top, and mpg ran around 20, instead of at least 25 and often 30 mpg on my 10:1 DE. I do drive it hard, it sees a fair amount of 6000-7000 rpm range otherwise I might actually get mileage above 30 mpg. I also replaced the cat and still have a bit of a NOx problem but that's another issue.

I have a second B13 now and its mileage is pretty poor (also ~20 mpg) despite plugs, wires, cap, rotor, fuel filter (the one I took out was full of black goo) air filter, but thanks for the reminder, I haven't replaced the O2 sensor yet. I and am pretty sure no one ever has in 104k miles given its appearance.

I attribute some of that mpg drop to the JWT S3 cams, and driving a bit more in the upper 5-6k range a lot, but not enough I should see less than 25 mpg on an otherwise well-running DE. It's tuned by JWT for 91 octane US California pump swill, so it's probably a little conservative to avoid excessively lean running.

Dont know if this will help anything but I had a bad Coolant temp sensor which was making the car run very rich, causing bad idle and sometimes stalling.. Replaced that and $20 later fixed ALL of my issues...

Hmm, I guess I can take out the O2 and verify it using a propane torch. Loss of air after the maf can cause overfueling as well.

Just as a reference, what should the SR20VET mileage in an Xtrail hover around....easy driving? I am at 16L per 100Km atm.

thx

My X-Trail GT was not stock when I picked it up but even with mods I could manage around 10~12L/100km around town. Depends on how hard you drive it though. If you drive like your 'driving miss daisy' around, you should see atleast 550+ Km from a tank.

The other thought I just had was also checking the drive by wire throttle body is clean and functional as well ;)