E39 525i M54 Cold Rough Idle

[Foxhole Norman]

Hey lads, still trying to resolve this cold idle issue I have with my car, it's only when it's dead cold and only rough until it drops to idle RPM's. I've replaced the entire CCV System, new Rocker Cover and gasket, MAF, both intake boots, Spark Plugs, Brand new DISA Valve yesterday, both pre cat Lambda Sensors with bosch units. Not sure where else to go, I keep getting the same two Bank 1 and 2 lean codes on Carly and the odd thermostat heating fault, I'm sure the thermo is due replacement as it doesn't always stay at 90°, but only colder. Would a faulty thermostat cause it?

[318is-joe]

Doubt the thermostat would cause this, does it cut out when it's rough ever?
What do you mean by banks 1 and 2 - a 525i is a straight six, banks are usually used for V engines. Unless the Banks are inlet and exhaust cams, in which case I'd be looking at the camshaft position sensor first, then valve timing.

[mcung13]

It looks that you are getting too much air in if both banks are lean.
Bank 1 is cylinders 1 to 3 and bank 2 is cylinders 4 to 6 on M54 engines.
Look for vacuum leaks.
There are capped off vacuum ports at the back of the manifold. One of the caps had fallen off on my 530 and this caused lean codes to come up.
It could also be cracked vacuum hoses or intake boots.

I found it by removing maf and cable tied a rubber glove over intake boot. Then I disconnected one of the vacuum hoses going to F connector on the intake boot and got friend of mine who smokes to blow smoke in from the F connector.
Smoke was coming out at the back of the manifold.
After replacing the cap, he was able to inflate the rubber glove by blowing in the F connector.
Proper ghetto method of finding vacuum leak, but it worked.

[rebel.ranter]

Dodgy injectors and coils can cause problems in the cold.

[Foxhole Norman]

Cheers for the replies lads, much appreciated, have some points to start at!

Dodgy injectors and coils can cause problems in the cold.

The coils and injectors were all running well within working parameters according to INPA but I can swap over some coils from my 528 and see if that does anything!