RPM dip and dive
I have a 2007 E92 with 114k miles on the odo. I recently replaced the plugs around 90k miles..... This week I was on a long (500+ mile) trip and got off the interstate after about 3+ hours of continual driving. While sitting at the light, my car started to shake/shudder and the RPM guage was dipping from it's normal idle of 650rmp to below 500..
The car has never done this before and is fairly well maintained... It occassionally will shake a little just after it's been started especially after sitting all night in the cold.
I know ignition coils should be able to last until ~150k miles, but does anyone think this could be the issue??
Or could it be something like the "winter gas" switch over??
ps... I also use a bottle or two of Techron roughly every 3k miles... last usage probably 2k miles ago.
('07 E92 328xi / '08 E83 X3)