Random misfire codes on all 6

[marcusbingham]

2003 330xi 105,000 miles

The engine was running rough with the check engine light on. I did some of the basics (oil change, spark plugs). I was still rough. Seems the air intake boots were in bad shape so I replaced thouse. At this point, the car is running better going down the road, and idles fine at first, but after an extended idle, it begins to run rough again and throughs on the engine light. The code reader indicates random misfires on all 6 cylinders. Any ideas on where to look next. Is it a vacumn problem and how can i tell?

[witeshark]

I wouldn't rule out coils and ignition wires.

[marti5]

Rotor cap may be on its way out or as WS mentioned leads/coils

[marcusbingham]

Thanks for the posts. Here is an update. Vacumn system appears to be sealed up. The coils and wires are giving correct voltage to the spark pulgs. However, the idle problem persists. I get codes from my Peake R5 / FCS -3 code reader as follows:

E3 - O2 sensor adaptation limit Cyl #1-3
E4 - O2 sensor adaptation limit Cyl #4-6
F2 - Misfire - Cyl #5
F1 - Misfire - Cyl #4

My local mechanic claims that the fuel system needs to be reset by the dealship, that it has adapted to runnin gwith the vacumn leaks and needs reset now that they are fixed. Has anyone ever heard of that? Any other suggestions before I take to the dealship 2 hours away?

[witeshark]

Maybe you could retest with new O2 sensors/

[dcuse32]

Sounds like you might have a hose leaking air for the compression. I just had the same problem with my car. There was a small hose on the top of the engine under the cover right by the air flow sensor. I had the same codes when i ran a scan. I thought initially it was the ignition coil but i could hear air leaking from that point. Do a sound test first and see if you are leaking any air. If that is not the problem check the coil and follow this video.

YouTube - BMW E46 M3 Ignition Coil Replacement and Cylinder Misfire

YouTube - BMW E46 M3 Ignition Coil Replacement and Cylinder Misfire