Never does it at idle or low RPM, but over 3k and there is a very bad misfire.

'08 535i with 84500 miles.

 

Are you burning a little too rich? Check for o2 sensor codes.

 

Questions:

Tuned or Stock? If so what tune?
When were the coils and spark plugs last changed?
What plugs do you have (Bosch plugs suck on the tune)?
Did you ever have a carbon cleaning done to the valves?

These are the common questions when diagnosing the causes of misfires. I just got rid of a misfire that wouldn't replicate under specific conditions except for cold idles. I determined that since my exhaust was black that its possible I needed a carbon cleaning. Since the cleaning the car felt amazing.

Pull the code so you know what cylinder is misfiring and inspect the spark plug. Make sure you torque the plug down to 17 lb-ft pounds or it will misfire like crazy.

If the plugs look good then swap coils around with another cylinder and note what cylinders you swapped. If the misfire moves then its the coil.

Replace parts in this order: Plugs, Coils, carbon cleaning then injectors.

Rare cause is bad DME. Very unlikely but it happened to a couple 335s.

Last but not least if you are in dire need of a valve cleaning you will have the left exhaust pipe coated in black and possibly a plug tip.

I hope it works out in the long run. Those misfires are a pain in the butt.

 

Agree with PB. I had a misfire and finally got the CE light and when I had a look with the software it was number six cylinder. My plugs had around 45k on them so I just replaced all of them and swapped #4 coil with #5 and mine was fixed. My car is also has a JB4 and I have recently heard you should change the plugs much sooner than the recommended 45K. I guess I'll go to 35 now. How many miles do you have on your plugs?

 

Spark plugs have to be done every 15k, some say coils at 25k

I replace both at 15k. I am on a Cobb Aggressive Tune.

You can get Okada (SP?) Plasma coils but they are 1000 bucks and you can keep them for 45k on a tune with no problems.

 

JB+
I bought the car at 60k, I personally haven't changed them.
No idea.
No.

I bought it from a BMW dealer, and it is a CPO.

Thanks for the info, I'll give it all a look.

 

Since I am going to be changing my oil this week, I went ahead and ordered all the stuff to do the plugs also. We'll see if that gets it done.

I'm really leaning towards the BMS catch can too.

 

Plugs changed, and WOW it runs better. I'm guessing these bay have been the original plugs.

 

Glad you were able to get it fixed. You'll probably be due for some new coils soon too. I had a interment misfire and decided to replace all six last week as a preventative measure. Now it runs like a champ and pulls like a freight train.

 

Plugs are obviously a wear item, but for us CPO owners, anyone have luck getting the coils changed out under warranty?