Bad Fuel Consumption Cont.

23rd January 2006, 06:06

Hello there people. After buying my VTS i thought 170 Miles to a full tank wasnt right. After speaking to a few people on here i relised i had a problem.

My car was booked into Citroen for a mate to check a few things over. While this was being done i asked him to Plug in Alexia and see if there was any faults, which could be causing my bad petrol consumption.

Turns out that the previous owner also had a De-Cat fitted with the exhaust. I was un-aware of this. My VTS is a 2002 and has 2 Lambda Sensors. (Been told these are also known as Up Stream, Down Stream sensors)

The main problem ive got is with a decat this shudnt be affecting my MPG so much! Damo has near on exact spec to me and he is getting 300 Miles to a tank.

Both the Lambda sensors have been 'Plumbed' back into the exhaust and manifold. If there is a problem why is my Engine Management Light NOT ON???

Was speaking to Simo about this and he mentioned a GMC Lambda sleeve. Nopt sure exactly what this is and how it works. Any Body Shed some light on this?

Really would like some help as petrol is costing a bomb!

1. If i put a cat back on and plugged Lambda sensors back into this would my petrol consumption go back to normal?

2. Over Fuelling so much, Is this damaging my engine?

Scott> Simo mentioned that you may know about this.

Thanks for reading people.

Mark

23rd January 2006, 06:20

If im right there are two Lamaba Probe one before the cat and one after the cat ....if there is a de-cat fitted both the probes are reading the same readings which whats causing you to use some much petrol .......

23rd January 2006, 13:40

the second lambda is there to see if the cat is doing its job, if not then the ecu light flags, the first is to check that the fuel mixture is right so that it doesnt melt the cat.

When you turn your car on, ign only ie no engine running, do you see the engine management light come on? as you should, if not then its possible the previous owner has removed the bulb for it hence no light.

The GMC lambda sleeve basically sheilds the lambda from everything and the second lambda thinks its seeing clean air so doesnt register a fault.

I would def be trying this first (only costs £15) but at the same time id remove the +ve from the battery for about 1hr to allow the ecu to reset to take the new settings.

It is quite possible that your first lambda sensor is fubar but reading within the relevant ranges (albeit a bit rich) which would explain the high fuel consumption. See if you can get ahold of a second hand one or get someone to test it to see if its reading properly.

Lexia is great assuming the operator knows how to read the values its producing (as apposed to just fault codes)

23rd January 2006, 13:51

infact, now that i think about it, if your car is in limp home mode, then it wont use the lambda sensor and will use just the base values in the ecu which = crap fuel econemy

23rd January 2006, 14:35

cant really expand on what the ratster has said

23rd January 2006, 19:54

Just checked the car and no there is no ECU Light on when IGN+?? So im guessing the previous owner has dissconnected this.

It is quite possible that your first lambda sensor is fubar but reading within the relevant ranges

So how am i suppose to get this checked or changed?

infact, now that i think about it, if your car is in limp home mode, then it wont use the lambda sensor and will use just the base values in the ecu which = crap fuel econemy

What you mean Limp mode? How can i get it out of Limp mode

Where can i get a GMC Lambda sensor from? How are these fitted any one got a pic?

Thanks alot

Mark

23rd January 2006, 20:22

suprisingly GMC sell GMC lambda sleeves lol

by replacing the faulty part (or in this case putting the second lambda in the sleeve then leaving the batter off for an hr) doesnt have to be 1hr but this makes sure its reset, then once the battery is back on and you drive the car it will self learn all again.

23rd January 2006, 22:51

i spoke to gmc a while ago but im sure they said you put the first sensor where the second one is, and then put the second one in the sleave. I have no idea if this will solve the problem but thats definately how the sensors should be.

23rd January 2006, 23:00

doesnt matter where the first lambda is, as long as the second lambda is isolated from open air and the exhuast

23rd January 2006, 23:36

Ok thanks mate. I will look into this.

24th January 2006, 01:17

Cant you check the Lamaba sensors are work by using a multi meter to see if the readings are switching ....when you disconnect it from the loom ?

24th January 2006, 01:19

Yeah so like i told you last night Sparkie if the readings from both Lamaba's are the same it gives wrongs signals to the ecu and runs rich .....definatly find out why you havent got a management light

25th January 2006, 18:18

just went to the petrol station and i had clocked 170 Miles to a full tank. Really not good!

Think im gona ring GMC later and enquire about the Lambda Sleeve!

Any way filled it up with Optimax this time see if theres a difference

25th January 2006, 22:18

if thats full tank (45litres)your looking at 17-18 mpg. I think ferraris can get better consumption than that.
I know this may be a daft answer but have you checked like tyre pressure and tracking, air filter, injectors etc? dont shout and scream at me if im stating the obvious tho

26th January 2006, 04:08

Just had brand new tyres put on so thats not a problem!

Other things shudnt be causing it this bad. Its deffo the lambda sensor.
Didnt get time to order the lambda sleeve tonight. Will do this tommorow!

23rd February 2006, 06:11

ive got exactly the same problem with my de-cat but my engine management light is on, wolze did tell me about the sleeve ages ago i need to buy one now

23rd February 2006, 07:09

me gets 50miles from £6 petrol

thats town driving and some thrashing...

23rd February 2006, 14:50

I had the same problem with my decat, got myself a sleeve from GMC and the full consumption has got a lot better but obviously it's still not exactly perfect with about 320 miles to a full tank (driving like my mum)

23rd February 2006, 19:08

Quote:

Originally Posted by Subtle

I had the same problem with my decat, got myself a sleeve from GMC and the full consumption has got a lot better but obviously it's still not exactly perfect with about 320 miles to a full tank (driving like my mum)

does it go on the lambda sensor on the de-cat pipe?

23rd February 2006, 21:23

My cat was part of the manifold mate, the sensor I put in the sleeve was the one that came from the lower part of the manifold (under the cat)