my 95 540i v8 six speed has started running rough on startup especially in cold weather. but now even when it is warm out the problem persists. once warmed up it runs fine unless one of the plugs has fouled in which case it continues on seven cylinders. the block was switched at 17k miles, so i don't think the block is an issue.

Chances are you need spark plugs and ignition coils. Pull out your coils and check for cracks in the boot. There is a possibility of another problem but that is most likely the cause. You can narrow down which cylinder is having the issue by pulling the plug for the ignition wires one at a time while its misfiring till there is no change in how the engine runs.

If that turns out to be the problem and you want to order replacement parts shoot us a PM and ill get you a price.




-Clay

Most of the time it is caused by a vacuum leak. It is a also possible that the injectors may need a good cleaning. We need to check for possible vacuum leaks first in the intake system.