dbond

I want to share my experience with troubleshooting poor performance of a N52. Keep in mind the vehicle has 135k miles on the clock, and has been taken care of: O2 sensors, plugs etc. @115k miles. Still, for the past 15-20k miles it performed rather poorly, not always but most of the time. It would kind of hesitate on acceleration, minor vibration can be felt throughout. It felt like it lost 20-30 horses... It was consistently poor performance but nothing that would jump at you on a test drive. One thing to note, it was worse on humid warmer days. And no errors what so ever. MPG was OK too.
I was baffled with this problem for a long time. Ran gas cleaners, changed air filter etc. so normal maintenance items were taken care of. Next on my hitlist were injectors and perhaps coils. I'm glad to report that I got it resolved by replacing all 6 coils. The vehicle now runs very well. So mark it, modern coils are a maintenance item. They apparently degrade slowly without misfires or throwing codes.

E60I

Congrats!

Where did you buy the coils and what kind did you get?

I have at least 4 extra coils that I have as spares. Unless someone on this forum can kindly show some of us how to measure them, I think I will eventually change all six at the same time like you.

StormTrooper

Do you get hesitations only when the engine is cold? I've had this symptom for quite some time now. I'm leaning towards the coils also.

mustaffalj

Bro, I got same sympton just lately, Change all 6 coils, new plug, still vibrate when cold start, finally took out O2 Sensor and spray with electrical contact cleaner and it work fine, no more vibrate, my ride N52, maybe need to change new 02 sensor,

pcy

When you start the car [in the morning], engine runs in open-loop mode and O2 sensor data is not used in that mode. During this mode, car runs rich and the secondary air pump (if equipped) is also activated to help engine warm up faster.

After the engine warms up, engine goes in to closed-loop mode. In this mode, O2 sensor data is used for air/fuel mixture ratio and other considerations.

In other words, for cold-start issues, cleaning O2 sensor won't do anything.

As for your case, without actually looking at the car, it's difficult to say what fixed the vibrations.

turboawd

great point, but when the car is in closed-loop, does that data get stored or influence how the car will start when cold and in open-loop?

pcy

No.
ECU uses live O2 sensor data in closed loop mode only.

dbond

I got a new set from eBay, Bosh 0221504470 which are the same BMW OE # 12137594937