fuel economy of Holden dinosaurs

[Ozix]

I had a 1997 Commodore ute, was using 14 l/100 km when I got rid of it
with nearly half a million on the odometer.
Also have a 2002 Statesman that uses less than 12 l/100 km, same driving
cycle, more or less same engine, transmission and diff ratio, despite
being 350 kg heavier than the old ute. Statesman has only done 150,000 km.
So I presume the old ute was worn out: lost compression, retarded valve
timing and maybe tranny slipping too. The old workhorse might last
forever, just gets less efficient when you hang on to it too long.

[Clocky]

Post by Ozix
I had a 1997 Commodore ute, was using 14 l/100 km when I got rid of it
with nearly half a million on the odometer.
Also have a 2002 Statesman that uses less than 12 l/100 km, same driving
cycle, more or less same engine, transmission and diff ratio, despite
being 350 kg heavier than the old ute. Statesman has only done 150,000 km.
So I presume the old ute was worn out: lost compression, retarded valve
timing and maybe tranny slipping too.

Those could be factors but if it drove fine it was probably just an
injector issue. If you had already replaced the injectors with those
cheap ebay ones sets then that was most certainly the problem as their
flow characteristics are completely random and shithouse.

The old workhorse might last

Post by Ozix
forever, just gets less efficient when you hang on to it too long.

My old VR Commodore had over 500,000km on the original running gear and
was still using 12L/100km stop/start and about 9L/100 in the highway. It
would still be getting that if it weren't for some clown in a Navara
pulling out in front of me and writing it off.

[Ozix]

Post by Clocky
Those could be factors but if it drove fine it was probably just an
injector issue. If you had already replaced the injectors with those
cheap ebay ones sets then that was most certainly the problem as their
flow characteristics are completely random and shithouse.
The old workhorse might last

Post by Ozix
forever, just gets less efficient when you hang on to it too long.

My old VR Commodore had over 500,000km on the original running gear and
was still using 12L/100km stop/start and about 9L/100 in the highway. It
would still be getting that if it weren't for some clown in a Navara
pulling out in front of me and writing it off.

I had changed injectors about 2 years earlier. Generally if one starts
pissing fuel, you get error codes for left-right imbalance on exhaust
sensors. And I had changed the exhaust sensors, MAF sensor, fuel
pressure regulator, DFI coils all sorts of stuff that might affect fuel
consumption.

[Clocky]

Post by Ozix

Post by Clocky
Those could be factors but if it drove fine it was probably just an
injector issue. If you had already replaced the injectors with those
cheap ebay ones sets then that was most certainly the problem as their
flow characteristics are completely random and shithouse.
The old workhorse might last

Post by Ozix
forever, just gets less efficient when you hang on to it too long.

My old VR Commodore had over 500,000km on the original running gear
and was still using 12L/100km stop/start and about 9L/100 in the
highway. It would still be getting that if it weren't for some clown
in a Navara pulling out in front of me and writing it off.

I had changed injectors about 2 years earlier. Generally if one starts
pissing fuel,

They don't have to "piss" fuel.

you get error codes for left-right imbalance on exhaust

Post by Ozix
sensors. And I had changed the exhaust sensors, MAF sensor, fuel
pressure regulator, DFI coils all sorts of stuff that might affect fuel
consumption.

Before you do any of that I hope you checked compression. What were the
readings?

[Xeno]

Post by Clocky

Post by Ozix

Post by Clocky
Those could be factors but if it drove fine it was probably just an
injector issue. If you had already replaced the injectors with those
cheap ebay ones sets then that was most certainly the problem as
their flow characteristics are completely random and shithouse.
The old workhorse might last

Post by Ozix
forever, just gets less efficient when you hang on to it too long.

My old VR Commodore had over 500,000km on the original running gear
and was still using 12L/100km stop/start and about 9L/100 in the
highway. It would still be getting that if it weren't for some clown
in a Navara pulling out in front of me and writing it off.

I had changed injectors about 2 years earlier. Generally if one starts
pissing fuel,

They don't have to "piss" fuel.

Indeed. If the injectors "piss" fuel, it would indicate they are stuck
open and that will, among other things, fill the sump with petrol.

FWIW, a pissing injector, ie. one that isn't giving a proper spray
pattern, will cause lots of incomplete combustion and send scads of fuel
down the exhaust to the Cat. That fuel will combust in the cat and
overheat it, one dead cat. Ergo, such a situation will trigger a
shitload of emission codes, hopefully long before that happens. And
you'll get ring wash which ensures a short ring life. Might even get
piston and bore scuffing.

In my experience, injectors typically get gummed shut and this occurs
most often when cold. As they warm up, expansion loosens matters and
they free up - until the next cold start. Had that precise situation on
my previous Corolla though I detected the misfire *by ear* immediately
after a cold start. Didn't occur on a hot start. Since the cat was in
open loop, no emissions codes were triggered.

Injectors also gum up at the nozzle. This can provide a restriction to
flow so that *less* fuel than demanded is injected. That will set up
enrichment of all injectors on that bank, if not the entire engine.

When checking fuel pressure regulators, it is necessary to check that
fuel pressure varies appropriately with MAP - and that is easily checked
with a gauge.

Post by Clocky
 you get error codes for left-right imbalance on exhaust

Post by Ozix
sensors. And I had changed the exhaust sensors, MAF sensor, fuel
pressure regulator, DFI coils all sorts of stuff that might affect
fuel consumption.

Sounds like the typical *parts cannon* treatment. All the above bits can
and should be *tested* for correct operation and not just assumed to be
faulty - *before replacement*.

Post by Clocky
Before you do any of that I hope you checked compression. What were the
readings?

Yup, compression readings for sure. If the engine is down on compression
it will have lost *efficiency* and burn more fuel to do the same job.
Vacuum readings are a good indicator of low compressions also, as are
cylinder leakdown tests.

[Xeno]

Post by Ozix
I had a 1997 Commodore ute, was using 14 l/100 km when I got rid of it
with nearly half a million on the odometer.
Also have a 2002 Statesman that uses less than 12 l/100 km, same driving
cycle, more or less same engine, transmission and diff ratio, despite
being 350 kg heavier than the old ute. Statesman has only done 150,000 km.
So I presume the old ute was worn out: lost compression, retarded valve
timing and maybe tranny slipping too. The old workhorse might last
forever, just gets less efficient when you hang on to it too long.

A compression gauge, cylinder leakdown set and a vacuum gauge would have
illuminated the *worn out factor*. Surprisingly, even in this era of
computer controlled everything, a simple old vacuum gauge can tell a
decent story. If the trans was slipping, you would know about it soon
enough - they die quick when that happens. What could be happening is
the torque converter lockup might not be happening or the TCL clutch
itself might be slipping. On those, the TCL operates on, IIRC, 3rd and
4th gears. They are problematical and I'm not sure if a TCL clutch
provides any feedback to the DCM to indicate slippage. If not, and the
TCL slips, your engine will be revving higher and the torque converter
sapping some power - hence higher fuel consumption.

At 500k km, I'd have been replacing the pre-cat O2 sensors - as a matter
of course. At that mileage they were, unless replaced previously, well
and truly time expired. Did you know the O2 sensors degrade to the lean
side? Guess what that does to your fueling? That's right, it richens the
mixture which leads to a higher fuel consumption.

It's all moot, the car's long gone.

[Daryl]

Post by Ozix
I had a 1997 Commodore ute, was using 14 l/100 km when I got rid of it
with nearly half a million on the odometer.
Also have a 2002 Statesman that uses less than 12 l/100 km, same driving
cycle, more or less same engine, transmission and diff ratio, despite
being 350 kg heavier than the old ute. Statesman has only done 150,000 km.
So I presume the old ute was worn out: lost compression, retarded valve
timing and maybe tranny slipping too. The old workhorse might last
forever, just gets less efficient when you hang on to it too long.

Utes have lower diff ratios so the engine is always revving higher so it
use more fuel.