Hi guys

Im experiencing some running issues with my zetec turbo. It been running really well for a while now however recently its started doing something really quite worrying. When decelerating off boost im seeing afr's of 10.8 for a split second then however it swings right round to 22.4 and will stay like this for far too long for my liking.

I have to deceleration fuel cut set too off so i am at a complete loss as to what could be possibly causing this. Its not just happening after boost but even when just pottering around at low speed and loads.

I have a small datalog that shows the boost situation.

Any pointers will be much appreciated