High fuel consumption

D.Slatford · Unread post by **D.Slatford** » 27 Jul 2003, 04:16

I'm reallly getting concerned with the fuel consumption of my '95 2.0i SX Xantia. For many months now, I'm only seeing about 20mpg from it. Getting quite expensive to run, not to mention concern over where all that fuels going! It used to return MUCH better mileage than this.
I've recently changed the plugs, HT leads, oil, filters and lambda sensor, all with no effect at all. It also has a slight misfire on idle, running a bit roughly.
The last MOT in Feb revealed that the cat no longer existed, which I thought was strange, particularly as the fuel consumption went up a few months prior to that. I have this feeling fuel may be escaping unburnt (and probably shot another cat) - is there a way I could diagnose this?
Also, anyone know how much the thing would be worth now? It's otherwise in a good condition, barring the faulty alarm and immobiliser. Wondering if I stand any chance swapping it for a diesel xantia...

AndersDK · Unread post by **AndersDK** » 27 Jul 2003, 04:48

I think your Xantia is running with choke all time -
- a common problem on PSA cars.
The ECU uses a separate temp sensor - to control fuel enrichment with cold engine.
This sensor should be found near/behind the thermostat housing - having a 2pole connector - flywheel end of head.
It used to be a BLUE coloured connector on BX'es - but may be different coloured on later generation PSA engines.
The sensor usually have approx 3.5Kohm cold - decreasing when hot.
Either the sensor or cabling/connector may be at fault.

D.Slatford · Unread post by **D.Slatford** » 27 Jul 2003, 06:53

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by AndersDK
The ECU uses a separate temp sensor - to control fuel enrichment with cold engine.<hr height="1" noshade id="quote"></blockquote id="quote">
Thanks, I'll check this out tomorrow. Consulting the Haynes manual, the sensor is still behind the thermostat housing, and still has a blue lead, however it seems to drive the needle on the dash, which itself does work fine. The temp is on average about 90deg C. Does the ECU also use this signal, or does it have another sensor? The schematics in the Haynes manual make no mention of the ECU here :/
I was wondering also if the stepper motor may play a part in this. I had the ECU diagnosed a couple of months or so ago, the cit garage reckoned it was all fine, but the stepper motor could do with being replaced. As that thing's quite expensive and I don't seem to be suffering the usual signs of wear (Which I think was excessive idling or erratic speeds, I have a slight misfire at idle causing the engine to splutter a bit) I figured they were probably just trying it on. Could a dodgy stepper motor affect fuel consumption?

AndersDK · Unread post by **AndersDK** » 27 Jul 2003, 08:26

<blockquote id="quote">quote:<hr height="1" noshade id="quote">... The ECU uses a separate temp sensor ...<hr height="1" noshade id="quote"></blockquote id="quote">
- which is NOT used for anything else.
The Xantia Schematics are incomplete - you won't find anything on the Xantia's ECU wiring in Haynes.
The sensor is located elsewhere then - try rear/front of head.
Don't think the stepper motor can cause rich running - fuelling is controlled by ECU on the injector.
If the mpg figure went bad after service work in a garage - they may have fitted a new cambelt out of timing. This is becoming a common problem - for all car makes.

D.Slatford · Unread post by **D.Slatford** » 28 Jul 2003, 05:59

<blockquote id="quote">quote:<hr height="1" noshade id="quote">If the mpg figure went bad after service work in a garage - they may have fitted a new cambelt out of timing. This is becoming a common problem - for all car makes.
<hr height="1" noshade id="quote"></blockquote id="quote">
You've got me thinking now. This DID all start up after I had the cambelt (and fuel filter, oil etc) changed over a year ago. A week after that it failed to start a few times, and has probably idled badly since. I don't recall seeing poor MPG before then either.
I'm not able to verify this myself - can anyone reccomend a garage around the Wakefield area, or able to help out? Can't afford the dealership (only cit garage I know of) as I'm yet again out of work

Grr.

AndersDK · Unread post by **AndersDK** » 28 Jul 2003, 19:15

Try browse these 2 threads for help/garages.
You may email members directly by clicking their name.
Topic : Where is everyone from
Link : http://www.andyspares.com/discussionfor ... IC_ID=3503
Topic : Citroen Specialist in . . .
Link : http://www.andyspares.com/discussionfor ... IC_ID=3476