Insane Fuel Consumption

[Jolinator]

cars been running great recently , altho started playing up this morning, in traffic my idle was on the piss, almost as if the AAC valve was disconnected all the gether, idle hunting up and down, on the way home from work, i start my car, takes a while to start. and it was blowing flames the entire way home, even at grandma speeds, i can only assume my fuel reg has died?

before people ask, engine is RB20det

Fuel filter is new,

Injectors are clean,

new fuel pump, healthy fuel lines, car is extremly well maintained and i cant find any faults, Diagnostics shows no codes either

any help would be much appreciated

[BH_SLO32]

Hunting can normally be attributed to a faulty O2 sensor. The easiest test is when the car starts to hunt disconnect the O2 sensor and see if the idle stabilises. Poor fuel economy would also suggest a possible O2 sensor fault.

If the idle does not stabilise when the O2 sensor is disconnected check for an air leak. I would be surprised if it was not the O2 sensor based on the info you have supplied.

Let us know how you go.

Hope this helps.

Cheers

[Jolinator]

o2 sensor is in good conidition and is fresh and no intake leaks

[FOG35]

could be your afm?

[Jolinator]

afm readings seem fine on consult?

[Jolinator]

bump

[BH_SLO32]

What testing did you do on the O2 sensor? My bro-in-law's car had an aftermarket O2 sensor which was replaced with another aftermarket sensor of the same model and the hunting continued. I thought we could rule out the sensor but when I disconnected the O2 sensor when it was hunting the idle stabilised. Re-connect the sensor and it started hunting again. Hunting would only occur very intermittently. Replaced O2 with a factory unit and hasn't missed a beat.

This is the first thing the skyline manuals say to check for and then spark plugs and finally air leaks.

Hope this helps.

[Jolinator]

spark plugs are in servicable condition, 02 sensor, i was looking at on consult and it was swinging back and forth so i assumed it was happy, also it looks brand new, and when i had it out of the dump it was pretty fresh,

i just took the car out for a run then, and it was great ,running fine,

one thing i can ad is that before it was playing up on the way home from work, it was requiring a few cranks to start up, it usually starts instantly which it has returned to doing,

have checked ignition timing also for the hell of it, 15-16degres at idle, so its spot on

car is running BP U98 only

been over the car with a fine tooth comb, from afm to the silicon joiners behind the front bar, checked all vacume lines, intake manifold gaskets are new, as are throttle body gaskets and bov gaskets, all exhaust gaskets are new aswell except manifold but i dont think thats relivent here

Edited June 18, 2006 by Jolinator

[Jolinator]

bump

[predator]

yeah, mine was same.. usually around 15L/100km, sometimes up to 18L.. Was tuned, everything checked, stuff replaced methodically, the works. In the end was a lost cause.

When replaced the motor everything is much more reasonable. Never found out what it was. Maybe it was just the signs of a dying engine?

Loss of compression, means not as much power being developed on every compression stroke = more fuel?

[tommo_190]

just to add to this .. my 1989 R32 GTR is running at an insane rate of about 24ltr/100km and is costing me a mint

the car is pretty much stock besides

-twin pod filters

-boost put up to 9psi

i've checked and there are no visible signs of fuel leaks, i have no idea where to start looking??

[Jolinator]

tommo you will need a different thread as you have a different car and i cant speak for your cars maintinence history/ condition. pred my car has spot on compression, all cylinders. cant remember the readings, but they were great

Edited June 20, 2006 by Jolinator

[predator]

so was mine.. but the rings were starting to get shagged so it didn't show up on a regular test (a leakdown would have shown different story).

Do you get much blowby?

[R32Abuser]

AAC valve?

[Jolinator]

i have had the car for over 2 years, and the catch can is compleatly empty with zero mist, even the lines are clean. very minimal blowby, doesnt use a drop of oil inbetween services

Edited June 20, 2006 by Jolinator

[Jolinator]

AAC valve causing flamage and backfires, i dont think so mine is superclean, i even went to the point of knocking the welsh plug out the back of it, taking the spring out , cleaning it etc, its fine,

its almosst like at random times i just decides to run super rich,

i once used a quater tank in 8 minutes, even tho the car was running fine

anyone else vote for the fuel reg?

Edited June 20, 2006 by Jolinator