Misfire cylinder 8

[Mbdurham17]

Hi all.

Well ended up getting the wife a new Denali a month ago so using her car as my highway runner for travel and back and forth on my long commute to the office so my M5 has been sitting in the garage since 12/1 after I got her all cleaned up.

Weather has been crappy here so been waiting on a pretty sunny day to take it for a drive and finally got that today.

I guess it was mad at me for letting it sit because I no sooner got out of the neighborhood and noticed it was running rough then got a drive train malfunction. Ran it for a little while seeing if it would clear up turned it off reset and it went away then tried again and back to limp mode.

I ran the diagnostics through my OBD scanner and it says misfire in cylinder number 8. I assume it's either a plug or coil pack issue but since it's just out of warranty (51k) I'd rather do this myself. The plugs were replaced at the dealer not very long ago so I figure coil pack and hoping that's what it is and not an injector but from what I read on here maybe the injectors are still under warranty if so.

Please let me know your your thoughts and also which cylinder is number 8? I assume it's one of the back not easy to get to ones of course but not sure which side

Thanks in advance!

[technician117]

Originally Posted by Mbdurham17

Hi all.

Well ended up getting the wife a new Denali a month ago so using her car as my highway runner for travel and back and forth on my long commute to the office so my M5 has been sitting in the garage since 12/1 after I got her all cleaned up.

Weather has been crappy here so been waiting on a pretty sunny day to take it for a drive and finally got that today.

I guess it was mad at me for letting it sit because I no sooner got out of the neighborhood and noticed it was running rough then got a drive train malfunction. Ran it for a little while seeing if it would clear up turned it off reset and it went away then tried again and back to limp mode.

I ran the diagnostics through my OBD scanner and it says misfire in cylinder number 8. I assume it's either a plug or coil pack issue but since it's just out of warranty (51k) I'd rather do this myself. The plugs were replaced at the dealer not very long ago so I figure coil pack and hoping that's what it is and not an injector but from what I read on here maybe the injectors are still under warranty if so.

Please let me know your your thoughts and also which cylinder is number 8? I assume it's one of the back not easy to get to ones of course but not sure which side

Thanks in advance!

New OEM Bosch coils are cheap. I buy them from Rockauto.com and use a 5% off coupon available from a quick Google search. Since they are cheap enough, I suggest buying at least one and swapping out #8. That cylinder is indeed the furthest one back. I'm 99% sure it's on the US drivers side.

Normal course of diagnosis would be to swap the coil to one that is further away and see if the code follows the coil before buying any parts. In this case, the coil is hard to access and why do the work twice if the new coil is so cheap.

[Mbdurham17]

Originally Posted by technician117

New OEM Bosch coils are cheap. I buy them from Rockauto.com and use a 5% off coupon available from a quick Google search. Since they are cheap enough, I suggest buying at least one and swapping out #8. That cylinder is indeed the furthest one back. I'm 99% sure it's on the US drivers side.

Normal course of diagnosis would be to swap the coil to one that is further away and see if the code follows the coil before buying any parts. In this case, the coil is hard to access and why do the work twice if the new coil is so cheap.

Thank you and yep I agree I ordered one from amazon yesterday for $25 and was delivered a few minutes ago. I'm going to swap out 8 and give it a shot. Thanks for the info from everything I've looked up I believe you are correct on which one is number 8

[Mbdurham17]

Swapped it out in about 30 minutes and all back to normal...yay! Guess I need to take her for a drive every weekend to make sure she doesn't get mad again lol

[SapphireM5]

Originally Posted by Mbdurham17

Swapped it out in about 30 minutes and all back to normal...yay! Guess I need to take her for a drive every weekend to make sure she doesn't get mad again lol

Congrats on the easy fix!! Enjoy