406oc.co.uk

1998 406 2.0 16v saloon 100,097 miles

recentley i noticed that my fuel economy on my trip computer had dropped from 26mpg to 23mpg town driving but i thought nothing of it as it has been getting a lot colder in the mornings recentley,
but working it out, after getting a few tank full's of no more than 270 miles which equalls about 16mpg, something must be horribly wrong, about 2,000 miles ago i serviced it with genuine filters, changed the cambelt and water pump, the tdc sensor, stepper motor, map sensor and oil pressure switch all because of another problem, so none of them can be too blame, also there are no fuel leaks, anyone got any ideas?

Oxygen Sensor in the eggsauce pipe before the CAT.

That's normaly favourite for a dramatic decrease in [American voice ON] Gas Mileage [/American voice OFF]

When it fails it allows the engine to run rich, sometimes you can notice an increase in soot from the eggsauce back pipe.

A Universal one should be OK at about £40.00? but see what some of the other Petrol owners think aswell

im certain its not the oxygen sensor, almost always this system would put the K light on, even if it didnt and the sensor was at fault the engine management would replace it with a substitute value of 4.5 volts indicating low oxygen content causing the engine to run lean, resulting in a loss of power and poor cold start, none of the symptoms i have