D
Donald Kay
I have read a few threads about O2 sensors and fuel consumption. I was
reluctant to jump on the band wagon but after the extreme measures by a
Subaru dealer to avoid this issue I thought I should offer my own
experience.
During a trip I noticed the fuel consumption increased dramatically. When
back in the city I found that fuel consumption was around 13litres/100Km
compared to my usual 10litres/100Km. (all figures in this post are with a
roof rack)
United Motors in Adelaide where I bought the car checked it several times
and reported nothing found. The next step was a fuel consumption test. At
their request I removed all accessories (roofrack/fridge etc) and presented
car for consumption test. They drove it 49Km and reported 11 litre per
100km. They then agreed that 49Km was hardly far enough. So I presented
the car for the whole weekend and they clocked up 400km of city driving (wow
my Subi the courier van) at 9.5litre per 100km.
Prepared to accept their test as possibly valid I had the mechanic take me
for a drive and I drove back - other than the fact that he never used 5th in
the suburbs we concluded our driving styles were similar.
We are now a year after the problem is reported, numerous visits to the same
dealer (the selling dealer) and no fix. As far as they were concerned the
car was fine.
I took the care to Ultratune in Adelaide City and happily paid around $70
for them to do a diagnostic. They reported that the vehicle was definitely
running significantly rich. They were kind enough to give me print outs
from 2 different gas analysers. They also reported the O2 sensor was
extremely slow and needed replacing. Further the engine management system
reported (and this is what United Motor claim to look at) that the engine
was getting 11% more fuel injection than it would expect to have to deliver
(learn). [For those not familiar with closed loop control the car adjusts
the fuel until the O2 sensor says the mix is correct. It learns how much
fuel this takes and uses that for its first guess and then trims it up. So
this means that it was taking 11% more fuel than the factory setting would
expect it to take before the O2 sensors report the mix is correct. But the
O2 sensor is reporting the mix is correct when the mix is wrong - but the
engine management system does not know this]
I took the report to the Subaru United Motors service manager who said he
would make some phone calls and sure enough I got a call after 6 in the
evening saying they would replace the sensor under warranty in a couple of
weeks time.
I let the next 1/2 tank run through without tracking cosumption. Then 10.2l
per 100Km which I am happy to call as good as new.
Over a year to get this problem rectified - I was at the point of getting
rid of the car and looking at other brands. Certainly shows your Subaru
dealer is not always competent to diagnose and fix your car. They do not
even pay for the 3rd party diagnosis or the hundreds of dollars of wasted
fuel.
Subaru is a great car. It is very reliable. But they do fail and the
dealers need to be alert to the possibility that the fault may not be with
the customer.
Another example of this is where I had mud build up on the
shocks/autolevellers on the rear, out of site, but rubbing on the original
tyres causing them to overheat and disintegrate. Fortunately at low speed.
(The Simpson desert between me and the nearest new tyres meant crossing the
Simpson without a spare!) Subaru flatly refused to make an incident report
for their quality system - I emailed photos and all. So no one knows how
often this happens - because no one records it when it is reported. I
wasn't even making a warranty claim they just made excuses.
Obviously Subaru is a great car despite the efforts of Subaru Australia and
their Dealer Network.
My advice - if you are not happy with the response from your Subaru dealer
get a 3rd party to check it out and if necessary demand service. Do not
accept "There is nothing wrong with your car" when you know there is.
Donald.
Keywords
Petrol gas fuel guzzling excess o2 O2 sensors mixture oxygen lambda milage
milege mpg
reluctant to jump on the band wagon but after the extreme measures by a
Subaru dealer to avoid this issue I thought I should offer my own
experience.
During a trip I noticed the fuel consumption increased dramatically. When
back in the city I found that fuel consumption was around 13litres/100Km
compared to my usual 10litres/100Km. (all figures in this post are with a
roof rack)
United Motors in Adelaide where I bought the car checked it several times
and reported nothing found. The next step was a fuel consumption test. At
their request I removed all accessories (roofrack/fridge etc) and presented
car for consumption test. They drove it 49Km and reported 11 litre per
100km. They then agreed that 49Km was hardly far enough. So I presented
the car for the whole weekend and they clocked up 400km of city driving (wow
my Subi the courier van) at 9.5litre per 100km.
Prepared to accept their test as possibly valid I had the mechanic take me
for a drive and I drove back - other than the fact that he never used 5th in
the suburbs we concluded our driving styles were similar.
We are now a year after the problem is reported, numerous visits to the same
dealer (the selling dealer) and no fix. As far as they were concerned the
car was fine.
I took the care to Ultratune in Adelaide City and happily paid around $70
for them to do a diagnostic. They reported that the vehicle was definitely
running significantly rich. They were kind enough to give me print outs
from 2 different gas analysers. They also reported the O2 sensor was
extremely slow and needed replacing. Further the engine management system
reported (and this is what United Motor claim to look at) that the engine
was getting 11% more fuel injection than it would expect to have to deliver
(learn). [For those not familiar with closed loop control the car adjusts
the fuel until the O2 sensor says the mix is correct. It learns how much
fuel this takes and uses that for its first guess and then trims it up. So
this means that it was taking 11% more fuel than the factory setting would
expect it to take before the O2 sensors report the mix is correct. But the
O2 sensor is reporting the mix is correct when the mix is wrong - but the
engine management system does not know this]
I took the report to the Subaru United Motors service manager who said he
would make some phone calls and sure enough I got a call after 6 in the
evening saying they would replace the sensor under warranty in a couple of
weeks time.
I let the next 1/2 tank run through without tracking cosumption. Then 10.2l
per 100Km which I am happy to call as good as new.
Over a year to get this problem rectified - I was at the point of getting
rid of the car and looking at other brands. Certainly shows your Subaru
dealer is not always competent to diagnose and fix your car. They do not
even pay for the 3rd party diagnosis or the hundreds of dollars of wasted
fuel.
Subaru is a great car. It is very reliable. But they do fail and the
dealers need to be alert to the possibility that the fault may not be with
the customer.
Another example of this is where I had mud build up on the
shocks/autolevellers on the rear, out of site, but rubbing on the original
tyres causing them to overheat and disintegrate. Fortunately at low speed.
(The Simpson desert between me and the nearest new tyres meant crossing the
Simpson without a spare!) Subaru flatly refused to make an incident report
for their quality system - I emailed photos and all. So no one knows how
often this happens - because no one records it when it is reported. I
wasn't even making a warranty claim they just made excuses.
Obviously Subaru is a great car despite the efforts of Subaru Australia and
their Dealer Network.
My advice - if you are not happy with the response from your Subaru dealer
get a 3rd party to check it out and if necessary demand service. Do not
accept "There is nothing wrong with your car" when you know there is.
Donald.
Keywords
Petrol gas fuel guzzling excess o2 O2 sensors mixture oxygen lambda milage
milege mpg