BMW Rough Run, Strange Fuel Trims

My 435i did something very similar when the intermediate lever spring popped off the back of the lever. I had a noticeable pop from the exhaust (modified) and like you said, it didn't feel like deal hole, but it certainly wasn't BMW smooth at idle. After exhausting fuel and air, I pulled the valve cover. I was about to put it back on when I noticed a little nick on the #6 intake cam lobe. The…

Trim weirdness on those can be due to 02 wiring being crossed front/rear. Quick test is to disconnect B1 sensor and watch code that sets.

Are the upstream 0 2 sensors wires crossed it’s very easy to do the plugs are the same and right next each other

Plugged cat?

Definitely would do back pressure test we had misfire on 45 and 6 last week in one was back converter starting to melt and clog up

Are there any odb codes?

Hi David, Being that there is an imbalance between the split exhaust, that leads me to believe there is a convertor issue on the rear 4,5, and 6 manifold convertor. A convertor melt down is possible, but what caused it? Any history of oil usage? The other idea that comes to mind is perform an injector balance test to determine integrity of injectors. Dirty or sticky injector could affect…

something I see quite often on Bmw’s is that the O2 sensors come loose. Not always loose enough to cause an exhaust noise or rattle, but give them a check, they will draw in air and mess with your trims as well as your head.

Did you replace the valve cover or just the valve cover gasket? BMW OEM parts or aftermarket? OEM coils or attermarket? Double check the gasket isn’t pinched in the right rear corner between the valve cover & head. Did you torque the valve cover bolts in the correct order & to proper spec according to SI? Did you pull the spark plugs and inspect them? Did you reset engine…

OE Valve Cover, AM Coils Gasket not pinched Valve cover torqued to spec Plugs were checked and had deposits (likely oil) Adaptations reset O2 Sensors were only disconnected during valve cover replacement and trim issues were there prior Check for and found no vacuum leaks Did relearn valvetronic limits post valve cover replacement

This could be a timing problem. What is the condition of the oil and filter, how much oil is in the engine? If not sure, flush the engine and change the oil and filter. You can also see with a scanner what the intake and exhaust cams are doing - desired vs actual position and if cam timing changes at all when rpm is increased. The vanos solenoids get plugged up and/ or fail intermittently and…

Had the same symptoms on a 07 328i, cylinders 4,6 miss fire codes when first start engine, verified the same condition as you did , checked all maintenance records all updates well maintained, when I first started the engine the next day I heard a rattle coming from the left side rear of engine between value cover and intake not metallic type more like plastic pieces loose then stop as engine…

Your upstream o2 sensor connectors are switched. That is what causes the fuel trim plus on one side and the minus on the other.

Split/mirrored trims have two common causes: the timing has slipped at the crank, or there is an imbalance in airflow through the engine…a lugged catalyst on one bank will usually cause very lean trims on the unaffected bank, and not a lot of correction on the ‘clogged’ bank… And, of course, the reversed O2s might cause this, but, if fuel is being dispersed evenly throughout the engine, then a…