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v6 ecotec guzzling fuel

mahooody

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my car fairly drink the fuel and i just had it serviced and mixures changes but still drinks it, i have herd that if your oxygen sensors are stuffed that they make the engine run rich, was just wondering how i can test the oxy sensors so i know for sure.

Thanks
 

TheForgotten

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not sure there is a way to test them.
also look at coolant temp sensor, as if this is stuffed, the ecu will think the engine is cold, and dump in more fuel
 

Harvs82

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Also make sure that your throttle body is clean, air filter is clean, perhaps replace your fuel filter. Also check fuel pressure, I have heard that this can cause fuel consumption issues also.

Coolant temperature sender is located just under the thermostat outlet, its the brass coloured piece, not the temp gauge sender, which has the small green wire attached to it. Only way to test it is to check for fault codes, or hook up the car to EFI Live and view the temperature from there.

Another thing to check is the thermostat itself. I've just replaced one on the parent's VS V6, temp gauge was sitting very low, and heating wasn't too good either. Engine ended up running too cold, ended up doing 14 litres per 100kms, all freeway travel!

With the thermostat replaced, economy was improved no end, averaging around 8 litres per 100kms again all highway driving.

I've also put some Holden Top End Cleaner into my fuel tank, which helps by cleaning the fuel injectors, and removing all the carbon and crap in the upper part of the cylinder and valves...
 
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kopper69

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There are many things that can lead to poor fuel economy. Many of them can be fixed by a simple diy service. Even oil change makes a big difference. With all these cheap options it surprises me that everyone starts with the oxy sensors. Alot more expensive then an oil change, and most times it a simple stab in the dark that they will improve fuel economy.

The computer in the VR/VS commodore is really not as dumb as some might think. Ill start from the beginning. Have a read.

Oxygen sensors basically give a certain resistance at a certain oxygen level. This resistance causes a voltage drop which is measured by the cars computer to determin what oxygen level it is working with. Now the computer is looking for a narrow reading. It has upper and lower limits. If the oxygen sensor fails, it will go outside these limits, and the computer will register an error code and engine light will come on. But the computer doesnt just use these values and give you really crap economy. It will subsitute in a known standard value, so the car will still give reasonable economy and performance until the faulty O2 sensor is replaced.

This means that unless you are getting an error code, the oxygen sensors should still be within their normal operating range, and should not be affecting your driving.

Now many users will say that their economy/performance has increased since replacing the sensors. And I believe them. I am just saying, start with the cheaper things. The basics are alot easier than the O2 sensors too.
 

mahooody

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ok thank you, some of the basic thing such as oil change, air filter, fuel filter etc were changed last week when i got it serviced and tuned. so i will change the thermostat and the Coolant temperature sender and see how i go from there.

Thank you heaps for the input
 

Don Sutton

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Gregorys / Scientific Publications manual details how to test the engine and air temperature sensor/s.

Not possible for home handyman to test the airflow sensor but is not usually dirty, thanks to being fitted after the aircleaner.

If the engine has done a high number of kms then the oxygen sensor will become gradually poisoned by phosphor from engine oil. Obviously if engine burns more oil oxgen sensor is poisoned quicker. Post above re oxygen sensor is in part correct in that the computer will detect an out of range reading but before this happens it will believe what it sees. The oxygen sensor is narrow band but there will be a percentage difference between real oxygen level and what is read. I would factor in oxygen sensors at about 100,000kms or if burns oil change sooner. Remember that blow by is sucked into the manifold which may or may not burn depending on engine operating conditions.
 

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i went through my whole car and did the o2 sensors last i should have gone the other way around im my case! it cost heaps! service, airfilter, plugs, leads tb clean nothing made a difference so i thought id live with it untill i thought one day what the hell i'll change em then bam cured the problem. considerable increase in fuel economy bugger all power increase but it runs smoother.
 
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