Using oil and fuel

[robgm]

So my Commodore VZ has 210,000km on the clock. Recently, under load, i heard this spinning up sound coming from the engine for a few days. This has stopped. But now the fuel usage has gone up by about 1L/100km. Also using oil - i have top up every few weeks. I checked under the engine top cover and can see oil stain on one of the coils, below PCV tube, and across part of the plenum. See photo. The car needs oxygen sensors done, i have done one, but the other is on top of the transmission so not got around to that yet. Any ideas what is the issue, before i take the plenum off to take a look at each cylinder.
Also, i did an oil change at the weekend. Only 4L came out. That was surprising because no "low oil" message came up? Is it an oil pressure sensor fault perhaps?

 

[Fu Manchu]

There’s no sensors on top of the transmission.
2004-2005 have two precat sensors just after the manifolds.

2006-2007 have precat and post cat sensors. Post cat located after the cats

 

[Fu Manchu]

Go to the how to section. Follow the PCV mod walkthrough

 

[robgm]

There’s no sensors on top of the transmission.
2004-2005 have two precat sensors just after the manifolds.

2006-2007 have precat and post cat sensors. Post cat located after the cats

Opps, i meant the sensor plug is on top of the transmission....need to drop the trans to unplug it. You're right, my Acclaim 3.6L 2004 has only 2 sensors.

 

[Fu Manchu]

No need to drop the trans. I’ve done it many times.

 

[robgm]

No need to drop the trans. I’ve done it many times.

How do i unplug? I can feel it with my hand but not enough space to unplug because the plug has catch i think so need to be able to push that in to release.

Is this the procedure, break the clip that holds the plug to gearbox?....
"Well nobody really gives you any good advice on how to change the driving side o2 sensor,as the passenger side is a piece of cake,jack up car use stands then take out bolts to gearbox crossmember lower jack giving you a tiny bit more room,the wiring harness is clipped to the side top of gearbox break clip off also,above passenger side sensor there is another on corner of engine there is a clip break that as it's plastic, then the wiring harness will have alot of slack to let the plug then dangle down to change,without too much trouble alot of different ideas,taking manifold,somebody says take cat off exhaust anyhow just hoping to make things easier for the next bloke who gets stuck cheers"
from page 3 VZ SS Oxygen Sensor Replacement.

 

[Fu Manchu]

One hand up in there. Thumb to press in the tab and fingers work it apart.
…To get the O2 sensor plug you do the same thing.

 

[robgm]

One hand up in there. Thumb to press in the tab and fingers work it apart.
…To get the O2 sensor plug you do the same thing.

Cheers - you must have done a few....originally i played with it for 5 mins and gave up....finding howto in this forum explaining to drop the trans. I'll practice on the easy one, passenger side. Then i'll take off the plenum, and PCV bits and pieces, and clean out the oil. Hope the engines not stuffed.

 

[robgm]

One hand up in there. Thumb to press in the tab and fingers work it apart.
…To get the O2 sensor plug you do the same thing.

I just tried again. I'm jacking up one corner only, the drivers-side front. I couldn't reach up to even touch it this time..i think i need to jack up higher. Is this the correct side to do it.....underneath the drivers side?

 

[Fu Manchu]

One on drivers side. One on passenger side.