My lovely 2.4 2005 Alphard has failed its MOT on emissions and we would like some help with what else it could be. It's failing on running too rich, fault code is P0171 running too lean. It has been coming up with that fault code for 18mths, we have had the following done;
* Airflow sensor changed (18 mths ago)
failed MOT last Friday on emmisions, so my mechanic did the following;
* MAF sensor changed
* spark plugs & air filter changed
* smoke tested for airleak and nothing is leaking
* cleared fault code
Retest today - failed on emmisions...
What else can cause it to be running rich - I'm thinking Lamda sensor but believe there is 2 of them, any ideas? Please help. I've 5 working days for a free retest!
TIA - Kate