4.8 Misfire Detected Checksum Failure

[Dsquared]

Hey guys - I'm new here but stumbled upon your great site looking for some help. Lots of great stuff here..Thanks! However, having some trouble with a 04 4.8is i bought recently at auction. I don't know much about it's history, but looks like it was taken care of. 115K miles on it.
It keeps throwing a "Misfire Detected Checksum Failure" code. I'm using the Peak OBDII tool to detect this. I think this is the equivalent to "Random Misfire". but i'm not exactly sure. Occassionally, I'll get a cylinder misfire as well, but that's inconsistent.

It starts right up and idles what i would consider rough for a BMW. I have owned several, none idle like this thing..but then again..none of them rumbled like a V8 Muscle Car either. Can wait to actually drive it.

Things I have tried already;

Replaced the plugs, coils and CCV's. I also have run fuel treatment to try to clean the injectors..not sure they are dirty, but figured it couldn't hurt.

Plugs had normal looking wear. All of the old coils tested out between 0.7 -0.9 ohms. New ones tested the same. Not sure what normal range is, but they were all consistent.

CCV's were obviously damaged (failed).

The vehicle spent it's life down south in Texas and Florida before I brought it up here to Northern NY. The guy i bought it from said there was no "SES" light on when it left his place. However, minutes after I started it up the day it arrived (late November ~30F) the light came on.

Before I start throwing more time and money at it, I thought I'd see if any of you have come across this with similar circumstances or have any ideas where to look next.


i appreciate any help or feedback.