repeated P0301 code
 

My 2003 X5 3.0 (170K) has repeatedly misfired and shown a p0301 code indicating a cylinder 1 misfire, I replaced the coil and the problem goes away only to reappear withing a month or two. Always cylinder #1. I've replaced the coil twice plus the original coil.

Any ideas?
______________

I pulled #1 plug and it looked worn and fouled, however #4 & 5 had broken center electrode ceramics. Signs of running rich with #6 looking the best. These plugs had only 70,000 miles on them I expected at lease 100K! So I just finished replacing all plugs, we'll see.

What plug are you running? My NGKs (Platinum4) also have about 70,000 miles on them and started to randomly misfire, mostly on cylinders #3 and #6. The misfires only occur on startups (as far as I can tell). I'm going to swap them out tomorrow and have a look

70k doesn't seem terrible. Cheap fix to do at that interval. NGK's @ $8ish/ea is only $48. I could live with that.

That said, are you using factory coils or aftermarket for the replacement? Any other stored or pending codes?

Hope your plug swap gets you at least another 70k without p0301, heck maybe you'll get to the 100k mark. :thumbup:

Edit: I usually use the NGK iridium single electrode plugs and have had really good luck with those on all my BMW's. Well, all except one... my custom turbo charged 318is e30. But that last one was my fault. Had to change those every 15-20,000 miles. :D

Definitely not complaining about the life of these spark plugs, but was curious (or a coincident) that the OP and I have about the same miles on the spark plugs when it start misbehaving. Still on the original coils.

I swapped out the original Bosch plugs at about 59K and installed these NGKs. The original plugs actually didn't look too bad - so that's why I had decided to give these NGKs a bit more time. I will give these a few weeks until doing a rescan to see if there's anymore misfire(s)

Check for a bad fuel injector. Had a misfire after replacing plugs and coil packs. Turned out it was my #1 injector.


Sent from my iPhone using Tapatalk

Here is a pic of my plugs - look close you will see broken ceramics on two They are NGK #3199 BKR6EQP

JIM

Looks like they are getting contaminated with oil. When was your valve cover gasket last done?

Yours are much worst than mine with the same mileage on them. At least mine are dried (oil free) and no broken ceramic.