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Author Topic: Deterioration in V6 fuel consumption  (Read 2640 times)

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jimbo_lad

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Deterioration in V6 fuel consumption
« on: 28 December 2011, 18:21:34 »

Hi Folks

I bought my Elite Estate 3.2 V6 in Aug 2006 and I’ve been a member of this forum since then. I haven’t posted much, but have often looked at it and found it interesting and informative. Current mileage is 86k.

However issues are beginning to accumulate.

Two years ago the Power Sounder kept going off which, with help from this forum, I diagnosed as a failing battery in the sounder itself.  Having sourced a replacement for this unusual battery, I was about to solder it into the existing unit, when I read here about the potential serious fire risk associated with old circuit boards in this unit.  The circuit board was showing signs of “tracing”, so I decided to disconnect the Power Sounder permanently, rather than repair. So that issue is sorted.

Pre Cats
Over the past 18 months the Exhaust Management Light has come on from time to time (usually a few months). The Pedal Trick revealed codes 0420 and 0430. Kevin Wood’s description of these codes and Catalytic Efficiency in the FAQ section were very helpful. The indication seems to be the Pre Cats are failing, but this doesn’t matter much so long as the main cats are OK – which they seem to be since the car passed MOT last April. So I'm ignoring this for now.

Falling Fuel Consumption

However the main unresolved issue is fuel consumption, which has fallen badly over the past 12 months. I used to get at least 32 mpg on a long steady run, but now only get about 24 under identical conditions with the same driving style.  MPG on shorter local journeys has fallen from 26 to 20 mpg.

The engine continues to start easily and run smoothly, although it now changes up through the gears more slowly. Running temp is around 85 deg, typical for the V6, and it doesn’t warm up any faster – so thermostat probably OK.

Tyre pressures are OK and it has been serviced regularly at main dealer.

The EML light came on again last Sept – codes 0420 and 0430 again present This time I booked it into the main dealer to look into the poor fuel consumption. The day before the booking I fuelled up and , by mistake, put in Premium 4 star. The EML went out within 5 miles – interesting, but could be a coincidence. I told the garage about the codes and emphasised I didn’t think this was associated with the poor fuel consumption – but they are the experts so I would value their advice.  Needless to say I left £50 poorer and none the wiser. They found codes 0420 and 0430 as I knew they would and had nothing to advice on the poor fuel consumption. “Bring it back if the light comes on again”

The light came on again in early Dec and codes 0420 and 0430 again present (plus 1613 due to missing Power Sounder). This time Premium fuel hasn't cleared the light, and even if it had I doubt if the fel consuption would improve since it didn't last time.

Yesterday I added some Redex Premium fuel additive – its supposed to help clean jets/valves/cylinder head etc – not sure if its likely to work and too soon to tell – however it might be more effective than another trip to the main dealer!

Could the codes 0420 and 0430 be associated with poor fuel consumption? Any thoughts on this, and what else to do would be gratefully received - I'd like to get to the bottom of this and improve fuel consumption.



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tunnie

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Re: Deterioration in V6 fuel consumption
« Reply #1 on: 28 December 2011, 18:25:01 »

What about the standard service items? When were they last changed?

* Air Filter
* Fuel Filter
* Breathers
* Plugs
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TheBoy

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Re: Deterioration in V6 fuel consumption
« Reply #2 on: 28 December 2011, 18:31:59 »

Initially check the condition of the air filter and plugs.  Then check standard service items.  Don't assume the dealer does the job properly, Vauxhall dealers are universally either incompitent or fraudulent.

If that doesn't show anything up, might be worth visiting Keviin Wood in Alton, to check it over with Tech2 (he'll know more than dealers).
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jimbo_lad

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Re: Deterioration in V6 fuel consumption
« Reply #3 on: 28 December 2011, 18:44:05 »

Thanks to Tunnie and TheBoy.

Service in April 2011 was intermediate, so last full service was Apr 2010 - when plugs/air filter/fuel filter all changed (at least that's what the invoice shows!). However I've only done 10k miles since then, so they should be OK, though I guess you never know?

I've checked the Air Filter and its a clean as a whistle.

By breathers, do you mean cleaning the V6 Crankcase breather set up?
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tunnie

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Re: Deterioration in V6 fuel consumption
« Reply #4 on: 28 December 2011, 18:46:59 »

Thanks to Tunnie and TheBoy.

Service in April 2011 was intermediate, so last full service was Apr 2010 - when plugs/air filter/fuel filter all changed (at least that's what the invoice shows!). However I've only done 10k miles since then, so they should be OK, though I guess you never know?

I've checked the Air Filter and its a clean as a whistle.

By breathers, do you mean cleaning the V6 Crankcase breather set up?

Yup!

Check the fuel filter, you can tell by looking its rough age. Bet thats not been changed!
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GastronomicKleptomaniac

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Re: Deterioration in V6 fuel consumption
« Reply #5 on: 28 December 2011, 19:00:55 »

Timing OK?
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jimbo_lad

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Re: Deterioration in V6 fuel consumption
« Reply #6 on: 28 December 2011, 19:18:52 »

Thanks, Tunnie - I'll get under the car tomorrow and see what I can make out. Should the label give an indication of age?
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tunnie

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Re: Deterioration in V6 fuel consumption
« Reply #7 on: 28 December 2011, 19:56:06 »

Thanks, Tunnie - I'll get under the car tomorrow and see what I can make out. Should the label give an indication of age?

Just look at its general condition, photo would paint 1,000 words  :y
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jimbo_lad

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Re: Deterioration in V6 fuel consumption
« Reply #8 on: 29 December 2011, 19:44:36 »

Checked out the fuel filter earlier today - here's a photo:



Seems in pretty good condition consistent with having been changed in Apr 2010. I would change it anyway if I had axle stands and suitable jack - but since I don't I've moved on to look at breathers and spark plugs.

I've just removed Plenum and will clean tomorrow. This is what it looks like on removal from the car:




These don't look too bad, but we'll see more when I dismantle and clean tomorrow!
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TheBoy

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Re: Deterioration in V6 fuel consumption
« Reply #9 on: 29 December 2011, 19:47:22 »

Yup, looks honest enough so far :y
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belldarr

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Re: Deterioration in V6 fuel consumption
« Reply #10 on: 29 December 2011, 22:07:11 »

Hi - It may be worth checking the handbrake cables - mine had corroded inside the plastic sleeving and therefore were not releasing the shoes fully, pretty unoticable apart from the fuel consumption as there was still a little bit of drag.  My handbrake still worked fine and I was unaware of the problem until my garage found this issue when they were doing the rear brakes.  Once fixed I found the car was nippier and the average consumption went up and I was getting around 25mpg with some town and motorway driving.

Regards

Darren
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jimbo_lad

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Re: Deterioration in V6 fuel consumption
« Reply #11 on: 30 December 2011, 14:18:15 »

Thanks, Darren - I'll check that as well.

Meanwhile I've spent the morning cleaning the Plenum. I was a bit disappointed it was relatively clean - here is the inside of the Throttle body and Plenum before cleaning:



However one of the pipes on the breather bridge was well blocked with pale brown emulsified oil - see below:



We used a novel way of cleaning this narrow tube - started with pipe cleaners then used a syringe to squirt carb cleaner through under pressure - worked a treat - see video clip showing third squirt:

http://s1091.photobucket.com/albums/i398/jimbo_lad/Omega%203_2/?action=view&current=MVI_1971.mp4

Hopefully cleaning this will make a real difference -time will tell. Does anyone know what this tube actually does? (its the narrowest of the 4 tubes at the rear of the Plenum and goes down the rear of the engine on drivers side).

One other thing we noticed was the fact that the plenum differed from the version shown in the maintenance guide. My car (2001 vintage) has the extended 2 part breather bridge (mentioned in the guide as a later variation to the 2003 engine
described). However, my model doesn't have the vent housing shown in the guide and instead has the assembly shown in the second photo above. We took this apart and cleaned - it wasn't very dirty and there weren't any  breather holes of the type shown in the guide - unless I've missed something?

Now need to reassemble and test.

Thanks for the help so far - I'll keep you posted on progress.

Jim
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Webby the Bear

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Re: Deterioration in V6 fuel consumption
« Reply #12 on: 30 December 2011, 15:14:23 »

Thanks, Darren - I'll check that as well.

Meanwhile I've spent the morning cleaning the Plenum. I was a bit disappointed it was relatively clean - here is the inside of the Throttle body and Plenum before cleaning:



However one of the pipes on the breather bridge was well blocked with pale brown emulsified oil - see below:



We used a novel way of cleaning this narrow tube - started with pipe cleaners then used a syringe to squirt carb cleaner through under pressure - worked a treat - see video clip showing third squirt:

http://s1091.photobucket.com/albums/i398/jimbo_lad/Omega%203_2/?action=view&current=MVI_1971.mp4

Hopefully cleaning this will make a real difference -time will tell. Does anyone know what this tube actually does? (its the narrowest of the 4 tubes at the rear of the Plenum and goes down the rear of the engine on drivers side).

One other thing we noticed was the fact that the plenum differed from the version shown in the maintenance guide. My car (2001 vintage) has the extended 2 part breather bridge (mentioned in the guide as a later variation to the 2003 engine
described). However, my model doesn't have the vent housing shown in the guide and instead has the assembly shown in the second photo above. We took this apart and cleaned - it wasn't very dirty and there weren't any  breather holes of the type shown in the guide - unless I've missed something?

Now need to reassemble and test.

Thanks for the help so far - I'll keep you posted on progress.

Jim

Is it the gearbox breather I've read about?
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tunnie

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Re: Deterioration in V6 fuel consumption
« Reply #13 on: 30 December 2011, 15:16:31 »

Er no, where is a gearbox mentioned?  ???

As mentioned in what you quoted its the breathers from the plenum!

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Chris_H

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Re: Deterioration in V6 fuel consumption
« Reply #14 on: 31 December 2011, 20:01:53 »

That's a big mpg hit and I'd be surprised if you could lose that much energy in binding brakes and not notice the smell or the boiling fluid.

Is yours an auto?  If so is it using top gear?

Just a thought...

BTW your intake is exceptionally clean IMHO.
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