Omega Owners Forum

Omega Help Area => Omega General Help => Topic started by: mkaminski100 on 05 November 2007, 10:10:55

Title: Petrol consumption (X20XEV)
Post by: mkaminski100 on 05 November 2007, 10:10:55
HI. I have Omega estate 2.0 16v (automatic gearbox). The petrol consumption is quite high. It’s about 15-16l/100km (ca18 m/gal, average 16,5 on the computer) in city and 9-10/100km on the highway (up to ca 30 m/gall, 26 average on the comp). I’ve changed the manifold (had a crack) and spark plugs (GM), fixed end exhaust box (few holes), changed lambda sensor (from Vectra 2.0 16V), and air flow sensor (form same engine), air filter and it’s still the same. I did the paper clip test and there were no errors (light didn’t flash).  
What I found odd is that when I press the throttle gently it goes down to 7.5 m/gal, and when I press it hard (to the floor) it goes to 7.1m/gal.
I don’t know if this is normal consumption or if I have to check my car again.  I had a Vectra with the same engine and the petrol consumption was 26 m/gal (city) and up to 41m/gal on the highway.  It’s about 30% less than Omega.
If there is any leakage from exhaust (before the lambda sensor), will it be shown on higher lambda sensor reading?
I've checked 2 sparkplugs (first and last) and both are almost white without any black spots or oily marks.  I will check remaining two today. I wanted to change all fuel injectors (with the rail with petrol pressure regulator), but if sparkplugs are that clean, I think it might not be the problem.
I dont have more ideas. I will check the compression soon (waiting for tool).
Is there anybody around Reading (30-40 miles radius) who can check it using Tech-2, or any other cable to find out if everything is ok with this car.
Title: Re: Petrol consumption (X20XEV)
Post by: Craig_R on 05 November 2007, 10:16:12
james had a problem with his old 4 pot 2.0l it was drinking fuel it got a lot better after he changed something to do with the coolent system i think it was the water temp sensor.

Just to give you a guild my 2.0l does about 40-45 mpg on petrol on a long drive at about 65 to 70 Mph
Title: Re: Petrol consumption (X20XEV)
Post by: Abiton on 05 November 2007, 10:20:29
What year is the car?  The coolant temperature sensors tend to read low with age, causing overfuelling. Tech1/2 should be able to tell you if that's the case.
Title: Re: Petrol consumption (X20XEV)
Post by: mkaminski100 on 05 November 2007, 10:27:50
It's the 1999 (NOV) so one of the first post lift ones.
I was also thinking about this sensor, but read that when it;s faulty (not broken, but reading lowered temp) I should have problems with starting up the engine when it;s cold. Isn't it?
Where can I find it?
Title: Re: Petrol consumption (X20XEV)
Post by: Abiton on 05 November 2007, 10:40:43
No I think it'll start from cold OK, but possibly have trouble hot starting 'cos of the excess fuelling.

But...when you say you paperclipped it and got no flashes, that makes me wonder whether you got this right, 'cos on my '96 at least, you see code 12 (test initiation) repeated continuously, even with no faults.

The sensor is at the back of the engine, below the DIS-pack, access not nice...

EDIT: Your clean spark plugs goes against my CTS theory anyway.
Title: Re: Petrol consumption (X20XEV)
Post by: Craig_R on 05 November 2007, 10:45:21
you dont get code 12 three times with later 2.0l 4 pot omegas, its a 4 digit code not a 2 or 3 digit one it threw me for ages as mine is a w reg facelift with a 4 digit read out when paper clipped
Title: Re: Petrol consumption (X20XEV)
Post by: mkaminski100 on 05 November 2007, 12:05:59
It's the same with old lambda sensor. Theoretically it works fine so there will be no error, but it idle on “high” and will make you ECU supply more fuel all the time. Then you have to connect TECH2 to find you a current reading.
I was told that the same think might happen with the coolant temp sensor. It works but somehow, instead of giving the right temp (ex 80) it will supply a false, lowered reading (ex 40). It won’t be shown as an error.  
It might be that when the sensor is broken, the engine goes into a “faulty” mode omitting faulty sensor and assuming that the temp is low. Then I would have a start up problem. I think that because the sensor is just lowering the temp, the ECU is giving just bit more petrol and that’s why everything is ok (no errors, clean sparkplugs). I hope that this might be a problem as I don’t have any other ideas…

What do you think about actual consumption at 7.1-7.5 when accelerating? Isn’t it too much? When I had a Vectra it was going down to 13-14 when accelerating with “heavy foot” and 20 with normal. The lowest I could get was 9m/gal with 4 people and pedal on the floor.
Regarding paperclip test “CraigR” has explained the thing. As far as I know, if there is no error, the light will not flash.
Title: Re: Petrol consumption (X20XEV)
Post by: theowletman on 05 November 2007, 13:47:18
I have had both manual and auto X20XEV Omegas. The auto was significantly heavier on petrol around town and on short journeys, 18 - 20 MPG. On the motorway it was reasonable at 35mpg. However my current car 1995 2.0 CD manual returns 25mpg around town and 40 - 41mpg on a run at steady 65 to 70 mph.Take it to a friendly MOT station and ask if they will do an emission test on the car, they have the gear.
Title: Re: Petrol consumption (X20XEV)
Post by: mkaminski100 on 05 November 2007, 16:04:02
How can I check this sensor?
Do you know anybody around Reading (London, in radius of 40 miles) who can check my car using Tech-2 and does the emission test?  
I begin to think that this is normal consumption and I can’t really do anything with it. Or maybe there is somebody else with the same engine (and automatic gearbox) who’s Omega needs less petrol than mine…
I know that I will have to put an LPG installation this year. Fortunately it’s only £600 for third generation (LPG injection).
Title: Re: Petrol consumption (X20XEV)
Post by: ians on 05 November 2007, 16:47:34
I think those consumptions are too high.   My 3L auto does c 25 mixed town driving and I reckon 30+ on a cruise, you should be doing better.

It might be worth cleaning out throttle body/ICV/breathers, replacing the (cheap) gaskets to ensure no leaks.
Are air, fuel filters recent?
Title: Re: Petrol consumption (X20XEV)
Post by: mikkethealarmguy on 05 November 2007, 22:46:19
a 2.0l 16v i once owned and used as a taxi
was great on fuel for an auto.
the 3.0l i have at the moment is pretty good too
far better than the 3.0l 24v senator i just scrapped
which was juicy !
probably due to me doing 120 in it everytime i got on a decent  stretch lol
Title: Re: Petrol consumption (X20XEV)
Post by: mkaminski100 on 06 November 2007, 07:09:35
There is no problem with throttle.It's clean as well as pipes and idle control. Do you think that there might be any conjunction between dirt throttle/ breathers etc and high petrol consumption?
Air filter was changed recently but I don't know when the fuel filter was replaced (again - if it would be clogged then the engine would have less power).
I need to chcnge the camshaft cover gasket as it's old and leaking (oil around spark plugs, and on the side of the engine).
I am waiting for the GM gasket and GM oil filter.
Title: Re: Petrol consumption (X20XEV)
Post by: tunnie on 06 November 2007, 07:38:04
make sure the exhaust is good and tight, no leaks. I noticed a 3-4 mpg improvement with the exhaust sealed correctly.

basics too like tyre pressurs can increase it by 1-2 mpg.

My facelift 2.2 manual does 34mpg with the cruise set at 85...

Over a mixed run it will average 31mpg
Title: Re: Petrol consumption (X20XEV)
Post by: mkaminski100 on 06 November 2007, 15:25:26
I have already changed the manifold, and checked exhaust. I can’t find any black spots (soot). I will have to check the manifold once again, but doesn’t have any crack and its ok on the top of the gasket (will have to check the bottom once again).
What bothers me is the air recycle system. When starting, I can smell unburned petrol and I think that it might be from the valve (or its ok).  It stops after few seconds. I will check it within few days.
I begin to wonder if it's not normal, as so many people confirm that manual needs much less petrol than automatic.  
Do you think that the petrol filter might have anything to do with a high consumption?
Title: Re: Petrol consumption (X20XEV)
Post by: JamesV6CDX on 06 November 2007, 18:02:22
Check the obvious first - are there any fault codes? Is the engine getting up to temperature?
Title: Re: Petrol consumption (X20XEV)
Post by: mkaminski100 on 06 November 2007, 21:47:06
As I said before: NO fault codes, new thermostat (engine is getting to 90 degrees after 10-15 minutes and is keeping this temp).  
I want to do a TECH2 check but just don't want to pay 40 pounds in Vauxhall to be told that "it's all OK, no faults, no error messages".
Title: Re: Petrol consumption (X20XEV)
Post by: cem_devecioglu on 07 November 2007, 12:06:48
Quote
As I said before: NO fault codes, new thermostat (engine is getting to 90 degrees after 10-15 minutes and is keeping this temp).  
I want to do a TECH2 check but just don't want to pay 40 pounds in Vauxhall to be told that "it's all OK, no faults, no error messages".
 

Hi,
10-15 minutes for 90 degrees is really long..Possibly you are in a very cold climate..Here in Turkey I remember last winter after thermostat change even in the morning with -7 celcius or -8  the engine reaches to 90 on the road within 3-4 minutes..
But in cold winter my normal 11.5 - 12.5 liter/100 consumption reaches 13.5-14 which are closer to your figures..(13 km road of which 1/3 is start stop traffic..and cold engine..


ps: mine is 2.5 auto 82 K miles..Also autobox condition can be important in that consumption
Title: Re: Petrol consumption (X20XEV)
Post by: mkaminski100 on 07 November 2007, 13:30:08
I don’t think that the engine can reach 90 degrees in less then 10 minutes (It takes few minutes to boil a litre of water). I am thinking about morning start when the outside temp is about 3-5 degrees.
If your consumption of 11,5-12.5 in city is calculated from petrol and not from computer then your car needs less than my Vectra 2.0 manual...
Oh, yes, condition of autobox is very important but is there any way to check it? Mine works fine and oil was changed recently (together with filter)
Title: Re: Petrol consumption (X20XEV)
Post by: theowletman on 07 November 2007, 13:45:50
Take the spark plugs out, if they are black and sooty your fuel mixture is too rich, they should be a light grey colour if all is well and running correctly. As I have said before ask a friendly MOT station to do an emissions test, our local station charges us £5 to do this test, it will tell you C02, lamda, hydrocarbons etc. This test is a lot cheaper than a diagnostic Tech 2. The Tech 2 is only as good as the person operating it, emissions test is so easy I could do it!!!
Title: Re: Petrol consumption (X20XEV)
Post by: cem_devecioglu on 07 November 2007, 13:53:35
Quote
I don’t think that the engine can reach 90 degrees in less then 10 minutes (It takes few minutes to boil a litre of water). I am thinking about morning start when the outside temp is about 3-5 degrees.
If your consumption of 11,5-12.5 in city is calculated from petrol and not from computer then your car needs less than my Vectra 2.0 manual...
Oh, yes, condition of autobox is very important but is there any way to check it? Mine works fine and oil was changed recently (together with filter)

my consumption mostly is dependent how much  I'm in hurry :)

the consumption figures is from the computer itself but I've managed to drop this below 10l/100 km
at the same route (home to job) with a grandma driving style (summer)  ;D

From what I've read on posts the check can be done by looking the small grindings and pieces in the autobox filter (basic-checked mine during filter change) ..However an experienced autobox specialist can see its condition with a 15 minutes driving..Or an omega owner who owned from 0 km..

This 10 minutes for heat up can only be in idle I think ..Still very long.. :-/

Sorry may be these dont help much..But still I think you have problem with thermostat..Did you changed CTS also ?

Edit: my highest consumption change occured with blanking the EGR , changing lambda sensors and changing exhaust completely..May be this will give little idea..
Title: Re: Petrol consumption (X20XEV)
Post by: mkaminski100 on 07 November 2007, 13:57:58
Sparkplugs are white like new. I bought them just before selling my Vectra and put them in Omega. They were a "cappuccino" colour (when taken from Vectra) then and after few hundreds of miles become white. Sparkplugs are genuine GM and are for this engine.
I assume that it's ok but anyway will have to do the emission test.
Title: Re: Petrol consumption (X20XEV)
Post by: Marks DTM Calib on 07 November 2007, 14:01:56
If you hold S and R pressed on the fuel computer stalk, what numbers appear in the MID display.
Title: Re: Petrol consumption (X20XEV)
Post by: mkaminski100 on 07 November 2007, 14:20:41
I will check my computer today. I did that before but just forgot to write down these numbers.
I’ve checked the filter and oil sump and there was nothing suspicious. No plastic pieces, nothing. Oil was clear (not as new but clear). There was a little bit of grey mud on the magnet but I was told that it’s ok when oil wasn’t changed from new.
When the engine is cold and I will press a full throttle, revs goes up together with speed. No clutch sliding. No “Christmas tree” on gear indicators. Only thing that bothers me is that it can change a gear just after depressing the throttle pedal. Friend of mine told me that every 2.0 does that.
My engine goes to 90 degrees in 10 min when in idle, but it takes 15 minutes in the morning. I drove another Omega and my old Vectra (with new thermostat from Wahler) and this time is always above 10 minutes. I know what you mean, and I can tell you that my thermostat is ok. It’s much better than my old one.
What is CTS?
I’ve unplugged the air hose from my EGR and when trying to open it (using screwdriver) engine goes crazy.  (Revs goes down and it starts shaking)
Lambda sensor was changed. It’s not new, but there was no change when the old one was replaced (no better, no worse). I think that the elastic joint between that double pipe and catalytic converter might be worth to change, but I’m not sure.
Problem with Vauxhalls is that it usually takes some time between fixing something and reducing consumption. ECU needs to adjust and or you can just wait or reset it and find that the consumption will go up for some time (in “adjusting” mode).
But still I like them to much to change it…
Title: Re: Petrol consumption (X20XEV)
Post by: cem_devecioglu on 07 November 2007, 14:37:20
CTS coolant temperature sensor..This gives the info to the ECU the coolant become hot and diminish the fuel amount in the injectors.But white sparks cancel that theory I think..

dont know how 2.0 EGR is but sure can be blocked by a thin metal ..Really worth checking may be stuck..
Title: Re: Petrol consumption (X20XEV)
Post by: mkaminski100 on 07 November 2007, 17:41:18
Numbers from MID: 012 3 24060.
I know how to check the sensor and will do it as well.
Don't think the EGR might be stuck, as I was was opening it wit a screwdriver and could see the engine reaction. AS soon as I left it, engine back to normal again.
Title: Re: Petrol consumption (X20XEV)
Post by: Craig_R on 07 November 2007, 18:29:15
Quote
CTS coolant temperature sensor..This gives the info to the ECU the coolant become hot and diminish the fuel amount in the injectors.But white sparks cancel that theory I think..

dont know how 2.0 EGR is but sure can be blocked by a thin metal ..Really worth checking may be stuck..

I have got my money on the Coolent Temp Sensor being knacked like it was on james old 2.0l 4 pot that was drinking fuel he said it was much better after he changed the coolent temp sensor
Title: Re: Petrol consumption (X20XEV)
Post by: cem_devecioglu on 07 November 2007, 18:36:56
Quote
Quote
CTS coolant temperature sensor..This gives the info to the ECU the coolant become hot and diminish the fuel amount in the injectors.But white sparks cancel that theory I think..

dont know how 2.0 EGR is but sure can be blocked by a thin metal ..Really worth checking may be stuck..

I have got my money on the Coolent Temp Sensor being knacked like it was on james old 2.0l 4 pot that was drinking fuel he said it was much better after he changed the coolent temp sensor

Agreed.Only this white sparks mess up the theory..
Title: Re: Petrol consumption (X20XEV)
Post by: Craig_R on 07 November 2007, 18:43:13
get a [size=20]GOOD [/size]photo of the spark plug end to let us see the colour of them
Title: Re: Petrol consumption (X20XEV)
Post by: mkaminski100 on 07 November 2007, 19:10:59
As requested :)
http://picasaweb.google.com/kaminski.marcin1/Swiece?authkey=ItD9bBnx6DY
They are not as clean as they were after long trip, and every one is darker on the one side and almost white on other.  I was just doing few miles a day from Monday is it might be a reason why they are black on one side.
So what do you think?
Title: Re: Petrol consumption (X20XEV)
Post by: cem_devecioglu on 07 November 2007, 19:19:55
this monday I see my sparks..Not similiar ..Yours are not totally black but sure darker than mine (7 K miles usage)..I dont think they are white..

Lets see what other members think.. :-/



Title: Re: Petrol consumption (X20XEV)
Post by: Craig_R on 07 November 2007, 19:41:07
To be honest there is nothing wrong with those plugs apart from the oil on them that would worry me alittle is there any oil at all in the spark plug wells ?

I would not class your plugs as white i would class them as normal.

I Still think its your Coolent Temp Sensor
Title: Re: Petrol consumption (X20XEV)
Post by: mkaminski100 on 07 November 2007, 22:24:20
Cam shaft cover gasket will be replaced this week - this is the reason of oily spark plugs. There is no oil on the spark cords.
As said before, when I came back from long trip they were white, but after three days of short trips, they look like that.
I will check the sensor. Do you know any other easy way to do it? I don't want to take it out of the engine.

There is something more that bothers me. When I start up cold engine (can be warm a little) I can smell unburned fuel  (not the fumes smell) from the manifold area but cant locate the source. It is only for few seconds and then its ok. It might be a air recycle system, but all hoses are ok.
Title: Re: Petrol consumption (X20XEV)
Post by: Kevin Wood on 08 November 2007, 00:03:46
Is that oil staining around the base of the insulator on those plugs or has the seal between the insulator and the metal surround started to leak?

Plug colour tells the story of what was happening for the last minute before they were removed. Also, with unleaded fuel it's less of an indicator. If the car has been idling for a while or started from cold they may well be sooty. If the car has just been driven under load at anything like the right mixture they will be white, or at least very clean with unleaded fuel. Those plugs certainly don't look bad, and a car with closed loop lambda control will put a fault light on rather than run with an incorrect mixture.

The ECUs coolant temperature sensor is worth checking IMHO.

Kevin
Title: Re: Petrol consumption (X20XEV)
Post by: Marks DTM Calib on 08 November 2007, 08:42:56
It would appear that teh MID might also have the wrong varient coding which could skew the consumption figures (its looks to be set to the wrong engine varient).
Title: Re: Petrol consumption (X20XEV)
Post by: mkaminski100 on 08 November 2007, 09:06:46
Tell me more... It's very interesting.
Title: Re: Petrol consumption (X20XEV)
Post by: cem_devecioglu on 08 November 2007, 09:24:06
Quote
It would appear that teh MID might also have the wrong varient coding which could skew the consumption figures (its looks to be set to the wrong engine varient).


 :o :o

something really new to me
Title: Re: Petrol consumption (X20XEV)
Post by: Craig_R on 08 November 2007, 10:04:39
It does look like yours is set wrong if its a facelift 1999

Here is the list of MID displays

http://www.omegaowners.com/forum/YaBB.pl?num=1167400261
Title: Re: Petrol consumption (X20XEV)
Post by: mkaminski100 on 08 November 2007, 10:42:16
I've seen that post, but there is nothing about the facelift (99). Only about pre facelift.
What code I should have and what does it mean?