P0171 and P0174 error codes - after succesfully passing MOT.

[YTL2024]

Morning all. Would appreciate the groups thoughts on the following:

My Z4 (03 reg, 2.5L petrol, 38k miles) recently failed its MOT due to emissions. Error codes P0171 and P0174 were showing. Took it to my garage, who identified that the air intake hose was split. Duly replaced, codes cleared and car passed the MOT with flying colours.

Before the repair, the car would run really rough when started from cold and would not idle well. Those issues have now gone and it runs like a dream.

Yesterday I was travelling at 70mph down a dual carriage way when the EML came back on. Hooked up the OBD when I got back home and same error codes - P0171 and P0174 (system too lean) - have come back up. However, unlike before, the car is running well.

So, could the cause be another leak somewhere in the engine? Or could I have a faulty MAF sensor?

I have ordered some MAF cleaner to see if that fixes the problem.

Anyone on the group has a similar experience to this?

[j3nks79]

Lean would indicate to much air so yes a split hose could be the culprit.

[Zedebee]

Check the new hose is on properly, all jubilee clips fastened etc. It is possible something has worked loose since fitting.