E46 2000 318i hunting on idle

You replaced all four 02 sensors ? Why ? It's important to note here, the very nature of the oxygen sensor sending these codes, without any other oxygen sensor fail-codes tells us the sensor is working as it should. What makes this code tricky is if this code appears by itself, there is NOT a monitored component that has failed, or it would be getting a code as well. In short, the engine is running lean, but the computer cannot tell why.
You replaced all those parts ? Time to take it to a qualified repair shop , because you have no clue an without the vehicle infront of use to test we don't either , especially after you replaced all those parts . Doing fuel pressure testing , hooking up a professional scan tool an viewing fuel trims (long &short term trims ) So do yourself a favor .

adding a breather to a pvc unit defeats the purpose of the pcv
it is there to allow excessive crank pressure to vent into the inlet manifold at variations in vacuum in the manifold and to allow those gasses to go through the combustion processes to reduce emissions
if you want to regress the engine , simply add a breathing filler cap to a rocker cover
BUT if you do that and the engine is EFI controlled then you will have fault codes coming up all over the place as a sealed sump is a part of the ECM control process You have not mentioned make and model but early fords ran like sheet if they had a bad crankshaft seal or leaking rocker cover gaskets

02 is not the problem you stated there where cel on when the car died. They could have been pending codes not related to the stall. Common on this car is crank, cam sen. If the crank fails it will stall and not show a crank sen fault code.

P0171 - System Too Lean Bank 1
Possible causes- Intake air leaks
- Faulty front heated oxygen sensor
- Ignition misfiring
- Faulty fuel injectors
- Exhaust gas leaks
- Incorrect fuel pressure
- Lack of fuel
- Faulty Mass Air Flow (MAF) sensor
- Incorrect Positive Crankcase Ventilation (PCV) hose connection Tech notes If the P0171 is combined with the P0174 code, it's very likely that the problem is caused by an intake leak. If there are no intake leaks, the next step is to replaced the air filter and clean the air flow meter. If the problem persist the front oxygen (O2) sensor may need to be replaced.

Hi there, i had a similar problem with my Legacy B4 RSK Blitzen, 2 litre Twin Turbo, Engine EJ208. Car would idle sort of ok when cold, after warming up it would idle erratically (idle hunting) and cut out sometimes. I notices the boost gauge hunting along with the RPM'S .I found it to be 2 faults. 1st fault - If you have an after market air filter and the car hasn't been mapped for the extra airflow past the MAF (Airflow Meter) then it confuses the ecu as its taking in un-metered air. Solution - Re-map car to take extra airflow or as i did, i took out the MAF and cleaned it with a can of Carb&Choke cleaner. It worked but still had rough idle.
2nd fault - Air could be in your cooling system. If there is air in the system then the engine temp sensor is reading hot/cold/hot/cold everytime an air bubble passes by, which will cause running problems. You may hear a gurgling or slushing noise in the car, which is air in the heater matrix. Solution - From cold open the header tank and coolant overflow bottle, un car untill engine warm and hold at 2000-4000 rpm untill you see air bubbles rise in the header tank. Make sure your hot air is turned on in the car and vents open. Do this process for 10-15 mins and when you think all air is out of system then re-fit header tank cap. Have a watering can at hand as you may require to top it up during bleeding. It will overflow but dont worry.


Only real problems Legacy's give are , Air Flow Meters, Knock sensors, and Lambda Sensors (O2 sensor). Hope this helps mate, keep us informed on how you get on.

remove and clean, idle air control motor. it may be clogged with carbon.(iac)

has to have pcv or somebody took it out for some reason but if u are getting oil in the air filter like that most likly u hav a broke ring on one of your pistons

p0171 indicates the system is running lean on bank 1,p0174 means the system is running to lean on bank 2 p1507 is an idle speed under run fault i'd suspect an air leak is the cause of your problem check air intake system for airleaks

You need a live data scanner to look at this when the problem occurs in real time, I could guess but that would waste your money and my time.

try disconnecting the air mass meter sensor if it runs better then ur air mass meter has failed had the same problem