High fuel consumption?

[tango]

Hi guys,

Recently purchased a 1.6 2010 Citi Golf. Car was last serviced on 88000kms at a private garage in February by the previous so I can't say what was actually done. It's on 94 000kms now.
On 2 tanks I've got 450 kms.
I thought this was a bit high so I had the car scanned. Threw out an intermittent lambda sensor fault which I replaced.
After replacing the sensor I've got 250 kms on just less than half a tank.

Is this normal? Or is there something I need to check out?

Thanks in advance.

[ICE King]

Hi

It's possible that it's normal (+-500km from a tank) , you also need to give info on your driving style. Do you redline the car alot , is that town driving or long road driving?

[OettingerTDi]

It's difficult without knowing how heavy your right foot is and what your typical daily commute looks like...

In my case, I have a 1997 1300 carb Chico used as a daily runner in about 50/50 ratio, highway versus suburbs, not going above 4000 rpm. I normally fill no more than 46 liters (49 liter tank) and get around 500 to 540km on a tank.

Guage wise, I get around 300k on the top half of the tank, and run the bottom part into the red before filling again.

Make sure that the air filter is clean or at least decent, and that your tyre pressures are correct, I have my own pressure guage and test pressures at home. Speed will also play a role, the exponential difference in air resistance between 100 and 120 is about 40%.

I hope this helps

[tango]

Thanks for the input guys.
I mostly do stop start driving. 15 kms a day but with traffic lights and medium traffic. Basically town driving.
I generally change around 3-4000 rpms

[OettingerTDi]

I think you are probably looking at fairly normal consumption there, around 10 liters per 100km average. Town driving is a killer and ambient heat does not help for low intake temperatures either...

On the other hand, the same 1300 Chico above has seen as much as 700km in pure highway driving.

[Dub rox]

It's difficult without knowing how heavy your right foot is and what your typical daily commute looks like...

In my case, I have a 1997 1300 carb Chico used as a daily runner in about 50/50 ratio, highway versus suburbs, not going above 4000 rpm. I normally fill no more than 46 liters (49 liter tank) and get around 500 to 540km on a tank.

Guage wise, I get around 300k on the top half of the tank, and run the bottom part into the red before filling again.

Make sure that the air filter is clean or at least decent, and that your tyre pressures are correct, I have my own pressure guage and test pressures at home. Speed will also play a role, the exponential difference in air resistance between 100 and 120 is about 40%.

I hope this helps

That and these cars have the airodynamic properties of a face brick. Still love it though, great little cars and easy to work on with parts redily available and cheap to maintain.

My 1.4i also gives about 500 km to the tank even if n drive it to the redline alot. Just to hear the intake sound it has at 5000rpm. Makes you want to be more "wind gat".

So i guess it's safe to say that you have the normal consumption for the mpi as you still have to concider that it has a cat on the zorst, were as the mp9 doesn't, adding more restriction. Driving style and the type of commute will also play a big role in this.

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[tango]

Appreciate all the comments. Thanks guys.

[panic-mechanic]

Mpi with O2 sensor fault. Do a search.

[Dub rox]

Mpi with O2 sensor fault. Do a search.

On that, found this little bit of info..........

Drivability Symptoms

A lambda sensor’s normal life span is 30,000 to 50,000 miles, but the sensor may fail prematurely if it becomes clogged with carbon, or is contaminated by lead from leaded petrol or silicone from an antifreeze leak or from silicone sealer.

As the sensor ages, it becomes sluggish. Eventually it produces an unchanging signal or no signal at all. When this happens, the Check Engine Light may come on, and the engine may experience drivability problems caused by an overly rich fuel condition. Poor fuel economy, elevated CO and HC emissions, poor idle, and/or hesitation during acceleration are typical complaints.

If the average voltage from the lambda sensor is running high (more than 0.50V), it indicates a rich condition, possibly due to a bad MAP, MAF or Air Flow sensor or leaky injector. If the average voltage reading is running low (less than 0.45V), the mixture is running lean possibly due to a vacuum leak or because the sensor itself is bad.

If the lambda sensor continually reads high (rich), it will cause the engine computer to lean out the fuel mixture in an attempt to compensate for the rich reading. This can cause lean misfire, hesitation, stumbling, poor idle and high hydrocarbon emissions (from misfiring).

If the lambda sensor continually reads low (lean), it will cause the engine computer to enrich the fuel mixture. Injector pulse width will increase causing fuel consumption and carbon monoxide emissions to go up. Constant rich fuel mixture can also cause the catalytic converter to overheat and it may be damaged.

If the lambda sensor’s output is sluggish and does not change (low cross counts & long transition times), the engine computer will not be able to maintain a properly balanced fuel mixture. The engine may run too rich or too lean, depending on the operating conditions. This, in turn, may cause drivability problems such as misfiring, surging, poor idle, and high emissions.

If a heated sensor has a faulty heating circuit or element, the sensor can cool off at idle causing the system to go into open loop. This usually results in a fixed, rich fuel mixture that will increase emissions.

Sometimes an apparent lambda sensor problem is not really a faulty sensor. An air leak in the intake or exhaust manifold or even a fouled spark plug, for example, will cause the lambda sensor to give a false lean indication. The sensor reacts only to the presence or absence of oxygen in the exhaust. It has no way of knowing where the extra oxygen came from. So keep that in mind when diagnosing oxygen sensor problems.

The lambda sensor is also grounded through the exhaust manifold. If rust and corrosion of the manifold gaskets and bolts is creating resistance, it may affect the sensor's output. To rule out a bad ground, use a digital volt meter to check for a voltage drop between the sensor shell and the engine block. More than 0.1v can cause a problem.

Lambda Sensor Checks

A good lambda sensor should produce a fluctuating signal that changes quickly in response to changes in the oxygen level in the exhaust. The best way to check the sensor is to observe the sensor’s output on a waveform scope or oscilloscope. A scope will display not only the sensor’s minimum and maximum voltage readings, and average voltage reading, but also its back and forth voltage oscillations from rich to lean.

Sensor output can also be read directly with a 10K ohm impedance digital voltmeter, or some code readers.

CAUTION! Never use an ohmmeter on a zirconium O2 sensor in an attempt to check the sensor because doing so can damage it. And never jump or ground the sensor’s leads.

The lambda sensor’s voltage reading should have a minimum reading of 200 millivolts (0.20 V) and a maximum reading of 800 millivolts (0.80 V). If the sensor reading is averaging low (under 400 millivolts) or high (over 500 millivolts), the engine may be running rich or lean because of some other problem.

If the sensor’s output voltage never gets higher than 0.60 V and never drops to less than 0.30 V, it needs to be replaced. The same is true if the sensor’s output is sluggish or doesn't change.

To check the sensor’s response to changing oxygen levels in the exhaust, first create an artificially lean condition by pulling a large vacuum line. When extra air is introduced into the engine, the sensor’s voltage output should drop to 0.2 V.

To check the sensor’s rich response artificially enrich the mixture by, if possible, clamping the return fuel line momentarily. This will force more fuel through the injectors and should cause the O2 sensor’s voltage to increase to 0.8 V.

If the sensor’s output fails to respond to the changes you've created in the oxygen level in the exhaust, it’s time for a new sensor.

Zirconia sensors can also be bench-tested by heating the tip with a propane torch while monitoring the sensor’s voltage output with a digital voltmeter. Connect the positive voltmeter lead to the signal wire (normally black) coming out of the O2 sensor and the negative voltmeter lead to the sensor’s outer shell. Then heat the tip of the sensor with the propane torch. The tip should be hot enough to turn cherry red, and the flame must enter the opening into the sensor tip. If you get a voltmeter reading above 600 millivolts (0.6 volts), and the reading quickly changes as you move the flame back and forth over the tip, the sensor is okay. A low reading or one that is slow to change means the sensor needs to be replaced.

Removing Lambda Sensors

Removing the sensor when the engine is cold will lessen the odds of stripping the threads in the exhaust manifold. Penetrating oil may be needed to loosen rusted threads. Once the sensor has been removed, the threads in the manifold should be cleaned before the new sensor is installed. Apply graphite grease to the sensor threads unless the threads are precoated.

Replacing Lambda Sensors

Everybody knows that spark plugs have to be replaced periodically to maintain peak engine performance, but many people don’t realise the same goes for oxygen sensors. As long the lambda sensor is working properly, there’s no reason to replace it. But after 30,000 to 50,000 miles of being constantly bathed in hot exhaust gas, a build up of deposits on the sensor tip can make it sluggish. If there’s enough clinker on the sensor tip, the sensor may produce little or no voltage at all. This produces a false "lean" signal that makes the computer think the engine needs more fuel, which it doesn’t but gets anyway. This creates a rich fuel condition that kills fuel economy and sends carbon monoxide and hydrocarbon emissions soaring. The engine may also experience additional drivability problems such as surging or hesitation.

The same kind of thing can happen if the lambda sensor is contaminated by deposits from sources other than normal combustion. It only takes a couple of tanks full of leaded petrol to ruin a lambda sensor (and catalytic converter). A lead-contaminated oxygen sensor will typically have light rust coloured deposits on the tip. Another source of sensor contamination can come from silicone poisoning. If somebody used the wrong kind of silicone sealer to seal up a leaky rocker box cover or manifold gasket, silicone can find its way into the engine and foul the sensor. Silicates, which are used as corrosion inhibitors in antifreeze, can also cause the same kind of poisoning. Sources here might include a leaky head gasket or cracks in the combustion chamber. Silicone deposits on the sensor tip will have a shiny white to grainy light gray appearance.

If the engine has an oil consumption problem due to worn valve stem seals, piston rings and/or cylinders, a build up of heavy black to dark brown oily deposits on the sensor tip can make it sluggish. If the deposits have a black powdery consistency, the fuel mixture is running rich. This may be due to the sensor already having failed, or it might be due to something else such as a leaky injector or a computer problem, or constant short journeys where the cold start system doesn’t have time to come off (open loop) known as housewives’ car.

Whenever you suspect a lambda sensor problem, the first thing you should do is scan for any codes that would implicate the sensor circuit. A code by itself doesn't necessarily mean the sensor is bad, however. It might be a wiring problem or something else. So always follow through with the diagnostic check to diagnose what’s wrong before you replace anything.

If you don’t find any codes, that doesn’t necessarily mean the lambda sensor is okay. In many instances, a sluggish sensor may not be bad enough to record a fault code but will still be causing an emissions or drivability problem.




Sent from my VFD 1100 using Tapatalk

[Dub rox]

Mpi with O2 sensor fault. Do a search.

On that, found this little bit of info..........

Drivability Symptoms

A lambda sensor’s normal life span is 30,000 to 50,000 miles, but the sensor may fail prematurely if it becomes clogged with carbon, or is contaminated by lead from leaded petrol or silicone from an antifreeze leak or from silicone sealer.

As the sensor ages, it becomes sluggish. Eventually it produces an unchanging signal or no signal at all. When this happens, the Check Engine Light may come on, and the engine may experience drivability problems caused by an overly rich fuel condition. Poor fuel economy, elevated CO and HC emissions, poor idle, and/or hesitation during acceleration are typical complaints.

If the average voltage from the lambda sensor is running high (more than 0.50V), it indicates a rich condition, possibly due to a bad MAP, MAF or Air Flow sensor or leaky injector. If the average voltage reading is running low (less than 0.45V), the mixture is running lean possibly due to a vacuum leak or because the sensor itself is bad.

If the lambda sensor continually reads high (rich), it will cause the engine computer to lean out the fuel mixture in an attempt to compensate for the rich reading. This can cause lean misfire, hesitation, stumbling, poor idle and high hydrocarbon emissions (from misfiring).

If the lambda sensor continually reads low (lean), it will cause the engine computer to enrich the fuel mixture. Injector pulse width will increase causing fuel consumption and carbon monoxide emissions to go up. Constant rich fuel mixture can also cause the catalytic converter to overheat and it may be damaged.

If the lambda sensor’s output is sluggish and does not change (low cross counts & long transition times), the engine computer will not be able to maintain a properly balanced fuel mixture. The engine may run too rich or too lean, depending on the operating conditions. This, in turn, may cause drivability problems such as misfiring, surging, poor idle, and high emissions.

If a heated sensor has a faulty heating circuit or element, the sensor can cool off at idle causing the system to go into open loop. This usually results in a fixed, rich fuel mixture that will increase emissions.

Sometimes an apparent lambda sensor problem is not really a faulty sensor. An air leak in the intake or exhaust manifold or even a fouled spark plug, for example, will cause the lambda sensor to give a false lean indication. The sensor reacts only to the presence or absence of oxygen in the exhaust. It has no way of knowing where the extra oxygen came from. So keep that in mind when diagnosing oxygen sensor problems.

The lambda sensor is also grounded through the exhaust manifold. If rust and corrosion of the manifold gaskets and bolts is creating resistance, it may affect the sensor's output. To rule out a bad ground, use a digital volt meter to check for a voltage drop between the sensor shell and the engine block. More than 0.1v can cause a problem.

Lambda Sensor Checks

A good lambda sensor should produce a fluctuating signal that changes quickly in response to changes in the oxygen level in the exhaust. The best way to check the sensor is to observe the sensor’s output on a waveform scope or oscilloscope. A scope will display not only the sensor’s minimum and maximum voltage readings, and average voltage reading, but also its back and forth voltage oscillations from rich to lean.

Sensor output can also be read directly with a 10K ohm impedance digital voltmeter, or some code readers.

CAUTION! Never use an ohmmeter on a zirconium O2 sensor in an attempt to check the sensor because doing so can damage it. And never jump or ground the sensor’s leads.

The lambda sensor’s voltage reading should have a minimum reading of 200 millivolts (0.20 V) and a maximum reading of 800 millivolts (0.80 V). If the sensor reading is averaging low (under 400 millivolts) or high (over 500 millivolts), the engine may be running rich or lean because of some other problem.

If the sensor’s output voltage never gets higher than 0.60 V and never drops to less than 0.30 V, it needs to be replaced. The same is true if the sensor’s output is sluggish or doesn't change.

To check the sensor’s response to changing oxygen levels in the exhaust, first create an artificially lean condition by pulling a large vacuum line. When extra air is introduced into the engine, the sensor’s voltage output should drop to 0.2 V.

To check the sensor’s rich response artificially enrich the mixture by, if possible, clamping the return fuel line momentarily. This will force more fuel through the injectors and should cause the O2 sensor’s voltage to increase to 0.8 V.

If the sensor’s output fails to respond to the changes you've created in the oxygen level in the exhaust, it’s time for a new sensor.

Zirconia sensors can also be bench-tested by heating the tip with a propane torch while monitoring the sensor’s voltage output with a digital voltmeter. Connect the positive voltmeter lead to the signal wire (normally black) coming out of the O2 sensor and the negative voltmeter lead to the sensor’s outer shell. Then heat the tip of the sensor with the propane torch. The tip should be hot enough to turn cherry red, and the flame must enter the opening into the sensor tip. If you get a voltmeter reading above 600 millivolts (0.6 volts), and the reading quickly changes as you move the flame back and forth over the tip, the sensor is okay. A low reading or one that is slow to change means the sensor needs to be replaced.

Removing Lambda Sensors

Removing the sensor when the engine is cold will lessen the odds of stripping the threads in the exhaust manifold. Penetrating oil may be needed to loosen rusted threads. Once the sensor has been removed, the threads in the manifold should be cleaned before the new sensor is installed. Apply graphite grease to the sensor threads unless the threads are precoated.

Replacing Lambda Sensors

Everybody knows that spark plugs have to be replaced periodically to maintain peak engine performance, but many people don’t realise the same goes for oxygen sensors. As long the lambda sensor is working properly, there’s no reason to replace it. But after 30,000 to 50,000 miles of being constantly bathed in hot exhaust gas, a build up of deposits on the sensor tip can make it sluggish. If there’s enough clinker on the sensor tip, the sensor may produce little or no voltage at all. This produces a false "lean" signal that makes the computer think the engine needs more fuel, which it doesn’t but gets anyway. This creates a rich fuel condition that kills fuel economy and sends carbon monoxide and hydrocarbon emissions soaring. The engine may also experience additional drivability problems such as surging or hesitation.

The same kind of thing can happen if the lambda sensor is contaminated by deposits from sources other than normal combustion. It only takes a couple of tanks full of leaded petrol to ruin a lambda sensor (and catalytic converter). A lead-contaminated oxygen sensor will typically have light rust coloured deposits on the tip. Another source of sensor contamination can come from silicone poisoning. If somebody used the wrong kind of silicone sealer to seal up a leaky rocker box cover or manifold gasket, silicone can find its way into the engine and foul the sensor. Silicates, which are used as corrosion inhibitors in antifreeze, can also cause the same kind of poisoning. Sources here might include a leaky head gasket or cracks in the combustion chamber. Silicone deposits on the sensor tip will have a shiny white to grainy light gray appearance.

If the engine has an oil consumption problem due to worn valve stem seals, piston rings and/or cylinders, a build up of heavy black to dark brown oily deposits on the sensor tip can make it sluggish. If the deposits have a black powdery consistency, the fuel mixture is running rich. This may be due to the sensor already having failed, or it might be due to something else such as a leaky injector or a computer problem, or constant short journeys where the cold start system doesn’t have time to come off (open loop) known as housewives’ car.

Whenever you suspect a lambda sensor problem, the first thing you should do is scan for any codes that would implicate the sensor circuit. A code by itself doesn't necessarily mean the sensor is bad, however. It might be a wiring problem or something else. So always follow through with the diagnostic check to diagnose what’s wrong before you replace anything.

If you don’t find any codes, that doesn’t necessarily mean the lambda sensor is okay. In many instances, a sluggish sensor may not be bad enough to record a fault code but will still be causing an emissions or drivability problem.




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That and then some hey. First thing one normally assume is that if the car is scanned and it throws out a 02 sensor fault that it has to be the sensor.

Turns out it could be something else causing it to fail instead of age, wich i think was the case here as you do not state if the sensor has been replaced before. Doubt your service record will state that...

Safe to assume the reason for replacement was age? Or is the car still having problems after the sensor was replaced? I rate you have the read as "@pannic" stated.

Sent from my VFD 1100 using Tapatalk

[panic-mechanic]

Ok Ok so before somebody else posts a massive extract from the internet and quotes himself on it about what an o2 sensor does - It is a now semi common issue we have seen on a number of MPI cars. As soon as that fault come up you can do what you want, change the sensor and whatever else you think might help, it doesn't.
They display either
Erratic idle behaviour
high idle all the time
too low idle all the time
jumps between fueling - now too rich - minutes later too lean.
Bad consumption.

The usual cure is replace with MP9 or put in aftermarket or if you are really a sucker for punishment - find another MPI.

[Dub rox]

Ok Ok so before somebody else posts a massive extract from the internet and quotes himself on it about what an o2 sensor does - It is a now semi common issue we have seen on a number of MPI cars. As soon as that fault come up you can do what you want, change the sensor and whatever else you think might help, it doesn't.
They display either
Erratic idle behaviour
high idle all the time
too low idle all the time
jumps between fueling - now too rich - minutes later too lean.
Bad consumption.

The usual cure is replace with MP9 or put in aftermarket or if you are really a sucker for punishment - find another MPI.

My first thaughts exactly. As i have read as much on the forum to assume this but did not think that it would apply here as it sounds like he was sorted? Maybe by luck or chance...

Sent from my VFD 1100 using Tapatalk

[tango]

Ok Ok so before somebody else posts a massive extract from the internet and quotes himself on it about what an o2 sensor does - It is a now semi common issue we have seen on a number of MPI cars. As soon as that fault come up you can do what you want, change the sensor and whatever else you think might help, it doesn't.
They display either
Erratic idle behaviour
high idle all the time
too low idle all the time
jumps between fueling - now too rich - minutes later too lean.
Bad consumption.

The usual cure is replace with MP9 or put in aftermarket or if you are really a sucker for punishment - find another MPI.

My first thaughts exactly. As i have read as much on the forum to assume this but did not think that it would apply here as it sounds like he was sorted? Maybe by luck or chance...

Sent from my VFD 1100 using Tapatalk

Panic is right about the erratic idle. Jumps between 9000 and 1100rpms. Guy that scanned it said this is normal??

After changing the sensor I haven't seen any improvement on consumption. I'm about to get to the red marking and I've done 480kms. Again is this about right?

Assuming the MPI is the problem, what is cost in going MP9 or aftermarket?

Thanks again guys

[Dub rox]

Ok Ok so before somebody else posts a massive extract from the internet and quotes himself on it about what an o2 sensor does - It is a now semi common issue we have seen on a number of MPI cars. As soon as that fault come up you can do what you want, change the sensor and whatever else you think might help, it doesn't.
They display either
Erratic idle behaviour
high idle all the time
too low idle all the time
jumps between fueling - now too rich - minutes later too lean.
Bad consumption.

The usual cure is replace with MP9 or put in aftermarket or if you are really a sucker for punishment - find another MPI.

My first thaughts exactly. As i have read as much on the forum to assume this but did not think that it would apply here as it sounds like he was sorted? Maybe by luck or chance...

Sent from my VFD 1100 using Tapatalk

Panic is right about the erratic idle. Jumps between 9000 and 1100rpms. Guy that scanned it said this is normal??

After changing the sensor I haven't seen any improvement on consumption. I'm about to get to the red marking and I've done 480kms. Again is this about right?

Assuming the MPI is the problem, what is cost in going MP9 or aftermarket?

Thanks again guys

Your fuel consumption sounds about right as you stated you do mostly town driving, get the cars ecu checked by a reputable mech and if it does turn out to be stuffed you have a couple of options.

Got a quote from gotech the other day and its about R5 k fitted for the normal ecu and R6 k for an ecu that allows for further mods on the engine later on. Both take one day to install if your there early.

It is just a matter of opinion realy that differs from person to person wich to fit and what make you will choose to suit your needs and pocket.

There are alot of makes out there to the likes of spitronics, dicktator and gotech to name but a few. Mp 9 will be much cheaper depending on who does the conversion but without the tunability.

Hope you get sorted



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[Wolf Mk2 16V]

10K's a litre is standard fare for Mk1/Citi Golfs....I've owned over 20 of them

[ICE King]

480kms and you at the red mark aka reserve which is good for at least another 50kms , So you getting 500kms+ urban

Don't be fooled by that red mark