Engine management light on - then off

alan s · Post by **alan s** » 02 Jul 2006, 19:44

At present, we have 2 Xantia 2.0i both with about 230K klms on them and both with a similar symptom.
If left idling for say 2 - 3 minutes, particularly when cold (but can also happen when up to temperature if the engine has been switched off for a while) the engine management light ("K" light) will come on.
If the car is then driven off at a fairly normal rate through the gears, within about 500 metres the light will go off and stay off.
My first thoughts were that it was possibly the lambda playing tricks as it has only just started doing it in the case of my car but did it right from the start on the recently acquired car of my sons. Of late, there has been a lot of playing around with petrol blends over here and I wondered if perhaps this was creating values slightly out of the range of the lamda particularly when there is potentially condensation burning off within the exhaust system.
Anybody struck this problem elsewhere?

Alan S

AndersDK · Post by **AndersDK** » 02 Jul 2006, 19:59

Petrol blends ?

- you mean mixed up with cheaper/lower octane ratings - or diluted with waste oils, paraffin etc ?
Its possible this could set off a wrong Lambda value - if the petrol mix is reluctant to burn properly in the engine (i.e. misfiring). But it wont contanimate the sonde (sensor) itself - as this is exposed directly to the exhaust temperature - VERY hot - burning off any residues.

Water in the petrol wont do this either. That will defo give you start troubles and erratic idle/running.

The problem could be (too) low octane rating - as then the knock sensor is signalling the ECU to retard the ignition timing trying to prevent the knocking (pinking). This is best diagnosed trying one of the octane improver additives around - or simply ethanol (alcohol). Or go for any super/high octane you can find locally (if any

).

Cant be long before an old fart like you have pin-pointed the problem

alan s · Post by **alan s** » 02 Jul 2006, 20:34

We're getting things like 95 octane and ethanol in the blends (up to 10% in places) whereas our standard ULP is about 91 or 93 octane. (Can't tell you for certain as I never use it)
As even my Oz spec BX16V states min 93 octane in the handbook, you'd have to think the 94/5 octane would have to be more than enough for a 2.0i Xantia 8 valve engine.
Where I am too, we get very high humidity most of the year, so condensation is always a major factor with 70 - 87% RH being quite common in Summer.

Alan S

Homer · Post by **Homer** » 03 Jul 2006, 12:26

Had an occasional warning light on a BX TZi, the bloke I sold it to had the fault codes read at a dealer and they reckoned it was the airflow sensor sticking.