Tanner Godby

I have a 530xi that recently had the oil separator go out. Burned a bunch of oil before it got changed. It ran rough after I changed it, and my codes indicated my cats were malfunctioning, which makes sense. I changed them. It still ran rough. I pulled the plugs, ugly as hell, changed those. Still runs rough, only 2 codes left. Misfire on all cylinders, and both banks too rich. What can cause this? My guess is the pre cat O2 sensors, since that is about all I haven't messed with recently, but I wasn't sure that alone could make it run this rough. Ideas anyone?

jtbgonesailing

If you managed to sucked enough crankcase oil past a defective CCV system, to foul a set of plugs and kill cats, surely you killed the pre cats O2 sensors also. How many miles on the car?

Tanner Godby

It has 180k, got it a year ago, and the service engine light came on a week after I bought it. Spent most of the year tracing down what needs replaced and getting to it. Ended up being a lot that was going when I got it. Have done the oil filter housing, and all that comes with that too. I just want it to run right. I did a full compression test when I was changing plugs. Full compression in every cylinder. At least there's that!

jtbgonesailing

Ok, with 180k miles on the odometer the O2 sensors are well past there prime moons ago. BMW recommends replacement at 100k miles on the n52 engine, most swapout both pre cat sensors around 120k miles. The n52 engine has proven itself pretty much bulletproof and I hope you still fall into that category. Change them out now and see where you are.

Did you receive any service records with your car purchase?

There is a new document on 5series now that you need to read, top to bottom. The author moved the document and his support from another forum. "So You Just Bought an E60", https://5series.net/forums/e60-discu...-begin-148359/

banglenot

Thanks for the kind words,

On the pre-cat O2 sensors for my N52 -- do you have any info on what I'd look for in INPA (for example) to measure the status of the sensors? Mine's turning 100K, and I want to put these kind of things on the maintenance schedule.

EDIT: spoke too soon. Good discussion here: https://bimmerprofs.com/management-lambda-probes/

MCS

Mass airflow sensor.. Oil kills those and it's the main sensor that adjusts air/fuel mixture.