2009 e61 Misfire, rough cold starts
I've been lurking around on this forum for a month or two now and after searching and searching for answers I've decided to make my own post outlining my problems with my 09 535xi touring. I bought the car about two months ago with only 54,000 miles. I had the intake valves cleaned of their carbon and a new alternator installed. The car has ran great up until the last few weeks. The first symptom I noticed was rough cold starts. After letting the car sit overnight, I come to start the car in the morning, and after about 4-8 seconds of cranking the car manages to stumble to life. This continued for the next few days. One day I came to start my car again after letting it sit overnight. The car stumbles to life and is misfiring horribly. The whole car is shaking. I turn off the car, wait ten seconds, start it again, and its running perfectly again. Strange. Over the next couple days I started to off and on feel a sudden jolt in the car as if it was misfiring just once while driving. I decided to change the coils and spark plugs, and the car ran better for a day or two, and then back to the same business. But since a week ago, everyday on my drive to work while cruising at around 70 mph, I get an "Engine Malfunction: Reduced Engine Power" message almost every time I hit roughly 3,000 rpm. I pull over and restart the car, and its business as usual again. Since I know the coils and plugs are good, could bad fuel injectors be my problem? I loaded up INPA on my laptop and read the codes and I have a knock code in cylinders 4 and 6. More recently, the cold starts have gotten much worse. The whole car is shaking for about 5 min, and then it smoothes out, but I can still feel slight hesitations/misfires after that. Any help would be appreciated. I can provide any INPA data you would like. BTW the car is fully stock except for DCI. Thanks in advance.