2007 Citroen C1 High idel Lambda emmisions

PPDoyle

Hi guys and Girls , i got my car serviced this month it required a new centre exhaust, which i had done, 2 years ago i replaced the cat when it went faulty, at that time i put new plugs in so this year i didnt bother doing the plugs but did do filters and oil. and went for NCT sadly it failed

low idel .......Co 0.1 Vol%.......above 30%................. PASS

840 (rpm)....HC 10ppm ......Above 0 ppm........................N/A

High Idel......Lamda 1.11....Not between 0.97 and 1.3..... MAJOR

2660 (rpm)..CO 0.02 vol%.............above 0.20%.........PASS

HC 9ppm ........ ........above 200ppm........................PASS

so i changed the plugs, added an petrol additive for emmisions and cleaned the PCV valve which was manky and had it retested , and it failed again again with the High idel Lambda, which changed to

High Idel......Lamda 1.12....Not between 0.97 and 1.3..... MAJOR

i am not showing any engine light on the dashboard and i dont know what to check now , any ideas ? i do have a spurious pre cat sensor for the car that i never used, i got it when the Cat acted up i dont have a post cat sensor , or maybe it could be that the new center exhaust i had put in isnt tight enough but i have no way to pump air into the system to see if their is a leak around it , and if it helps i have a car diagnostics ocb device that says it can look at emmisions readings from the onboard computer a quick look shows readings for bank one and 2 , but i dont understand them , i could put them up if that helps , any ideas would help thanks

John.G

High Lambda + low emissions often point to air ingress at exhaust, have a look at last NCT and see if emissions, especially the HCs were higher with normal lambda.