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[JamesV6CDX]

Right, did a test and realised why I'm so upset with the amount of juice I'm putting in the 2.5 V6 CDX Auto.

I filled the tank right up to the top in Cardiff, and drove VERY carefully to Barry Island and then back to Cardiff. Roads were quiet, there was a bit of stop start, but generally kept moving and I was careful on the gas.

The round trip was 29 miles, and when I got back I filled it back to the top. To my horror, it took 2 gallons - in my mind that means it's doing just under 15mpg!!!!!!

This is disgusting, my old CDX auto 2.5 would have done 24/25mpg on that run, which to be honest is a figure I would be more than happy with and can live with, but I can't live with 15/16!!

I need to investigate why this thing is mopping up sooo much petrol, and would appreciate some advice in the right direction! Breathers were done a couple of months ago (I appreciate they may need doing again so not ruling out).. and I'm aware the spark plug leads aren't brilliant (but not in too bad a way either.

The only other thing is that I've got a significant exhaust blow from a mid-section. Is there any way this could be contributing? If so, by how much?

I'd really appreciate some pointers on what to do!

Cheers
James

[JamesV6CDX]

The only fault codes are an immobiliser one (nothing to worry about - historic) .. and something relating to the EGR. I posted about it in a previous thread, and have checked all the connections as per Mark's advice, which are all solid.

Could this be having an impact on MPG?

[x25xe]

Blowing exhaust will upset Lamba readings so could be causing the engine to run rich.  Other things to think about:

1. Is the DIS pack OK?
2. You mention HT leads - if they are less than perfect - replace them.  Mis fireing is a risk not worth taking in my opinion.
3. Are the plugs OK?
4. Any vacum leaks
5. Binding brakes
6. Under pressure tyres

That is about all I can think of.

Fuel economy is the one thing that I do not like about the Omega.  I went on a trip to Devon at new year.  In my Cavalier, I can do the entire trip in just under half a tank (just under 30 ish litres(i tend to brim the tank)).  The Omega used half a tank getting there and I filled up again before going home.  It used the same again on the way home although the MID reported (for a short while) 35MPG.

Hope this helps in some way.

[Taxi_Driver]

Blowing exhaust will upset Lamba readings so could be causing the engine to run rich.  Other things to think about:

1. Is the DIS pack OK?
2. You mention HT leads - if they are less than perfect - replace them.  Mis fireing is a risk not worth taking in my opinion.
3. Are the plugs OK?
4. Any vacum leaks
5. Binding brakes
6. Under pressure tyres

That is about all I can think of.

Fuel economy is the one thing that I do not like about the Omega.  I went on a trip to Devon at new year.  In my Cavalier, I can do the entire trip in just under half a tank (just under 30 ish litres(i tend to brim the tank)).  The Omega used half a tank getting there and I filled up again before going home.  It used the same again on the way home although the MID reported (for a short while) 35MPG.

Hope this helps in some way.

All of the above sounds worth checking to me  

Other thing i thought of is throttle body....AA cleaned his a few weeks ago and reported about 3/4mpg improvement  

I was running on petrol this afternoon.....ran outa lpg   .....reset my mid and for 70 miles on the m4 roughly doing 80mph it reported pretty much bang on 30mpg......thats for my 2.2 tho.

Other thing is, did you fill back up at same garage and the same pump? There are differences between pumps of when the pump 'clicks' off. Your probably better off monitoring it over a month.....ie take the mileage now and again in a month and note how many gallons you put in it.....and work the av out that way  

[JamesV6CDX]

Yes mate. I did use the same pump. But you've a valid point, it's not possible to be 100% accurate I guess with my method. Still though, it's using a lot!!

Laidback also cleaned out my throttle bodies a couple of months ago, I remember seeing my face in them

I will check all of the above though... tomorrow is going to see an interesting exhaust repair using some thick steel and a rivet gun

[TheBoy]

Can you bodge exhaust blow so you can rule that out? That may well affect it, depending on where it is...

[sounds2k]

well the way I understand it, the EGR valve allows some of the exhaust gases into the inlet manifold ... in that way it means that the volume of fuel/air mixture is reduced so it runs leaner (less emissions) as a result - however this is only used on part throttle, on full throttle (and I believe idle) it isn't used. So a faulty EGR valve might be contributing to your problem, then again fuel used is surely related more to the injectors and thereby controlled by the ECU ....

[TheBoy]

well the way I understand it, the EGR valve allows some of the exhaust gases into the inlet manifold ... in that way it means that the volume of fuel/air mixture is reduced so it runs leaner (less emissions) as a result - however this is only used on part throttle, on full throttle (and I believe idle) it isn't used. So a faulty EGR valve might be contributing to your problem, then again fuel used is surely related more to the injectors and thereby controlled by the ECU ....

Its always a possibility, so I'd block egr, then can rule that out...

[JamesV6CDX]

Cool!

Jaime - the exhaust blow is on the back part of the right hand mid-section. I'm going to rivet a bit of steel over it and paste it, as a temp bodge to see if that's making a difference.

So you're saying blocking off the EGR could rule that Out? I want to do that. Didn't someone have some blocking plates?

[stuart30]

15mpg sounds like my 3.0ltr round town...the 2.5 estate ive just bought on a 100 mile run with about 30 miles of that stop start traffic jam returned constant of about 34/35 mpg and now ive done 100 odd miles of twon driving im looking at 26 mph ish.

Mind you it is manual box if that makes any difference. :-?


Is Upper Hatherley still a dive....

[JamesV6CDX]

Upper Hatherly??

[stuart30]

Upper Hatherly??

Never mind maybe wrong side of cheltenham for you some call it Up Hatherley..

[Marks DTM Calib]

Buggered exhaust will screw up the lambda sensor readings........its not EGR!

[JamesV6CDX]

Cheers Mark, will see if that makes a difference tomorrow.

I do know upper hatherly.... You originate from there?

[x25xe]

well the way I understand it, the EGR valve allows some of the exhaust gases into the inlet manifold ... in that way it means that the volume of fuel/air mixture is reduced so it runs leaner (less emissions) as a result - however this is only used on part throttle, on full throttle (and I believe idle) it isn't used. So a faulty EGR valve might be contributing to your problem, then again fuel used is surely related more to the injectors and thereby controlled by the ECU ....

Correct and this is why when the valve sticks open it knackers the idle.  It is related to the knackered exhaust I think.

[MartinP]

Cool!

Jaime - the exhaust blow is on the back part of the right hand mid-section. I'm going to rivet a bit of steel over it and paste it, as a temp bodge to see if that's making a difference.

So you're saying blocking off the EGR could rule that Out? I want to do that. Didn't someone have some blocking plates?

Even though Mark said it's not the EGR, I have posted 4 plates out today and have some left if you want one.

[tunnie]

that might explain why my new zorst showed an improvement in mpg...

Can't offer any technical advice on that James, but i am sure you'll fix it. But 15mpg is a bit crap!

[Andy B]

......

Even though Mark said it's not the EGR, I have posted 4 plates out today and have some left if you want one.

PM sent.  

[JamesV6CDX]

I need one urgently!! Sending PM..

[Martin_1962]

Upper Hatherly??

Never mind maybe wrong side of cheltenham for you some call it Up Hatherley..

I come from Twigworth originally!!!! (near Down Hatherly)