Intermittent amber engine management

[andydimbleby926]

I recently bought a 2009 4.2 X150. After a couple of hundred miles I had an amber engine management light. My local specialist said the error codes related to a weak mixture and they replaced 2 Lambda sensors. After the next tank top up the error message reappeared so they had the car a couple of days and checked for any vacuum leaks. When I got the car back it was fine....until I refilled the tank again. I’ve recently completed a couple of long journeys and on both occasions the light has gone off after a hundred or so miles....but I’ve refilled the tank again today and the light is back on! The car drives perfectly and on motorway runs is returning nearly 30mpg. Any ideas?

[J44EAG]

You say vac leaks were attended to, Andy. Were the small 1/8th ID rubber pipes around the throttle body area replaced? Any leak there can cause codes to be thrown.

If you have had Lamda sensors replaced, I`d suggest you might still have slight historical catalytic converter issues. These can often be helped by using a couple of cans of Cataclean additive in the fuel which loosens deposits and helps things get back to normal. This advice based on 15yrs of running V8 Jags. Cataclean may be found on Halfords shelves or on the internet. Use as defined on the instructions. Do not thrash the car whilst you have the additive in the fuel. Just run the car around gently and let it work its magic start to work through.

This type of fault can be stubborn to remove but doing the above frequently helps and may cure this type of problem completely. Just have patience with it and eventually you will find a fix. Try Cataclean as a first step.

Mike K

[andydimbleby926]

Thanks Mike. The vacuum hoses were checked but not replaced, so replacement might be a sensible precaution. I’ll give the Cataclean a go too.
Thank you. Andy