R34 N/a Using Alot More Fuel Than Usual?

[Dany]

My R34's has been using way too much petrol lately, I get about 200km's for $50, that's close to 17L per 100km. I cleaned the K&N air filter, tried both Shell V-Power and Mobil 98 Octane, but it didn't help.

Would anyone have any idea what the problem could be? I'm thinking it might be the spark plugs, I got the premium one's put in about 30.000k's ago and haven't changed them in a while. I change the oil, fuel filter & oil filter regularly.

Thanks for the help.

[SL33K]

Oxygen Sensor?

[BASHO]

Tried cleaning the AFM ? or like SL33K wrote 02 sensor , get an ecu fault code read shouldn't cost much and will likeley give you an answer without trying 50 fixes that don't work first.

[putraged]

check O2 sensor between the extractor and firewall. or get nissan consult and read the R34 service manual. the manuals basically covers the whole problems. PM me if u need the R34 manual copy.

[vidospace]

Plugs can also tell tales. If the car is running rich etc. Change the plugs but keep the old ones to show your mechanic (label them 1 - 6)

[mad082]

the first question has to be asked, how do you drive and what mods do you have? that can rule out pretty much all other things depending on the answer.

if you have mods like a bigger turbo, etc then you will always use more fuel if you like to give it the beans often.

also if you just drive lots of short trips and spend a fair bit of time with your foot down on boost. if you do like to boost it often then you aren't too far out of the range of what you can expect, however if you do lots of steady driving and don't spend much time in traffic slowing down and speeding up then that is a bit high and the o2 sensor is probably the main cause. this can be done with a multimeter. do a search to find out how.

how long does the car take to warm up (for the needle to come up to half way)? it should come up to temp within about 5 mins of driving (or 3 or 4kms). if it is taking much longer to do this then your thermostat needs replacing and that will get you better economy because you won't be on cold start enrichment so much. coming into the colder months this can become more of an issue as you can actually get to a point where the car pretty much never warms up so you use much more fuel.

[Hanaldo]

the first question has to be asked, how do you drive and what mods do you have? that can rule out pretty much all other things depending on the answer.

if you have mods like a bigger turbo, etc then you will always use more fuel if you like to give it the beans often.

also if you just drive lots of short trips and spend a fair bit of time with your foot down on boost. if you do like to boost it often then you aren't too far out of the range of what you can expect, however if you do lots of steady driving and don't spend much time in traffic slowing down and speeding up then that is a bit high and the o2 sensor is probably the main cause. this can be done with a multimeter. do a search to find out how.

how long does the car take to warm up (for the needle to come up to half way)? it should come up to temp within about 5 mins of driving (or 3 or 4kms). if it is taking much longer to do this then your thermostat needs replacing and that will get you better economy because you won't be on cold start enrichment so much. coming into the colder months this can become more of an issue as you can actually get to a point where the car pretty much never warms up so you use much more fuel.

I imagine he doesn't hit boost very often...

[Dany]

Thanks for the replies guys.

mad082, I don't hit the boost often since the car is non-turbo but thank you for the reply, I usually shift the gears around 2.5k's RPM's, I don't really drive hard.

I found a thread on how to test the O2 sensor with the paperclip method, so I will do this on the weekend. Only mods I have on the car is an exhaust system and splitfire coilpacks, I'll test the o2 sensor on the weekend, if that's fine, then I will try changing the coilpacks.

[Galois]

to check error codes you can use the following diy

http://www.skylinesaustralia.com/forums/Re...de-t266512.html

[Dany]

Well I changed the o2 sensor, no improvement.

Checked spark plugs and the fuel regulator, all good.

Checked the ECU for error codes but it comes up as code 55 = no error.

I get about 320k's per full tank before the fuel light comes on.

Anybody got any other ideas with what's causing this? Bad injectors? Vacuum leak?

[iseekool]

Fatter tires = more drag

Underinflated tires

Check for dragging brakes. Also check the park brake/handbrake.

Get your wheels re-aligned.

If your car is a manual - check for a slipping clutch

If your car is an auto get the automatic serviced.

Check the vacum line to the variable length intake manifold's acuator. This can cause the car to act sluggish at low RPMs and also lower the engine torque - therefore you will be pressing the accelerator more.

Ensure you are using light weight engine oil nothing heavier than 40 weight.