What needs fixing?

[w8stedYouth]

Hi all,
My 98 VT is playing with my head. 1st I thought the o2 sensors went- my car was running at 25.5l/100km after getting extractor installed, then on the way out to buy new ones it started reading as low as 8l/100km but mainly @ 10l/100km. I was very confused but thought it might have just fixed itself temporarily of course.

So in went the new o2 sensors and on my test drive started at 19l/100km but rose back up to 25.5. when the car got to temp. I made sure plugs were in correct way and they were as they would not have clipped in properly otherwise. So I loosened the sensors and retightened a few times while on the ramp until I got sick of it basically. It now starts at about 19l/100km and sttles at about 16. But if I let her warm up for 10min it will drop right down to8l/100km and get upto about 12l/100 on a 15min drive
I havent changed much apart from CAI. and thermostat(just replaced).
I have also cleaned my MAF sensor recently and changed sparks which always come out black and sooty even if in for 5 min?

What should I be looking at - Replacing ECU? Replacing Cluster?
Does a memcal tune fix my air/fuel mix or say if its running rich b4 would it still run rich?(Was just going to get a greenfoam chip and see how it went)

Also I never seem to register any faults on my dash even when the o2 sensors went which I find is weird. And which is why i Dont know what the hell to do.
All help is appreciated

 

[graham7773]

I doubt the O2 sensors were to blame to start with especially seeing they have made little difference to your problem. You will get various opinions here about what could be causing your motor to use excessive fuel. Might be time to bite the bullet and get your friendly Holden dealer to diagnose the problem. I would guess that whatever controls the fuel supplied to the injectors is in constant cold weather/temperature mode or possibly the fuel pressure regulator is not doing its job. One more idea, you cleaned your MAF sensor? Is there a chance you damaged it? If so, try to find a good one at the wreckers and replace yours as an elimination process.

 

[w8stedYouth]

No I used the good $25 MAF cleaner from autobarn, And followed instructions! I doubt the o2 sensors were needed aswell but paid for them already!

 

[DLFHUB666]

i was thinking you may have damaged your MAF sensor aswell

 

[devnull]

Is it merely reporting that usage or is it actually using it? How much do you get out of a full tank?

 

[w8stedYouth]

Is it merely reporting that usage or is it actually using it? How much do you get out of a full tank?

Well it reports it. I am not sure its correct because of inconsistancy when I put in o2 sensors, it seems to chew through the fuel atm wether it reads 8L or 19L/100km.

 

[FC50]

Well it reports it. I am not sure its correct because of inconsistancy when I put in o2 sensors, it seems to chew through the fuel atm wether it reads 8L or 19L/100km.

How about you fill it up
Drive it sensibly until the fuel light comes on
Fill it again taking note of how many litres and how many KLM's done
Put that data in here Metric Fuel Consumption Calculator
And then make an assessment.

At least then you will actually know what the fuel usage is.

 

[sedgewik]

you should know if your at he pump more often o2 sensors wont read prop if all the fuel isnt burning in cylinder (not enough spark) my cars got 120k did the rockers zorst cai etc was using fuel like it was going out of fashion.changed the plugs leads coils dfi fuel filter maff cleaned o2 sensors knock sensors injectors tps etc its using alot less fuel and going alottt harder and runing smoother dont regret the extras for the mods at all!!!every part made a noticable difference did all this for a cold start prob?