[BMWinAZ]

Ye olde e90 328i (2008) has 76k miles on the odometer, time for new spark plugs. I watched plenty of YouTube tutorials, read the Bentley manual front to back, made sure I had all the tools and ordered NGK plugs and Bosch coils (same as the old ones) from BavAuto. The goods came on Friday and today (Saturday) I got to work. Removing the cowl and engine cover was pretty easy and gave my OCD self the chance to clean the dusty back of the engine cover that I can't reach after a normal wash. Removing the old parts also was no big deal thanks to all the internet info out there. The plugs looked pretty worn and I am glad I changed them, the coils had not given me (or rather my wife whose daily driver the e90 is) any grief but I figured it would be good preventative maintenance to change them while all the engine cover stuff was off anyways. So I put all the new parts in place, torqued the plugs to spec and made sure the new coils were properly connected and seated. Up to this point everything had gone smoothly and within the expected time frame. However, I have two things to add to what everybody else has said in their tutorials: 1) most people complained about spark plug 6 being the difficult one to remove due to it's placement in relation to the engine brace, I found this to be number 5 which sits right under the brace and the two fat wiring harness looms. 2) Although the N52 does not necessarily require a special spark plug socket and I had a spark plug socket in my Craftsman socket set that seemed to be an ok fit, I nevertheless ordered a special thin-walled socket for under $ 5 from Amazon, and a good thing this was. When I tried the Craftsman socket it got stuck on the spark plug after I torqued it, so I had to undo the whole thing and then use the cheap, no-name socket which performed without fail through the entire process. Ok, now back to when my trouble started. After the complete install I hopefully turned on the car, it tried but did not start the engine. I tried again, same result: crank but no start. I assumed (correctly as it eventually turned out) that the coils are to blame. So I pulled all the new coils (which are the same brand and look identical to the old ones) and replaced them with the old ones. Now the car started but ran rough and idle somewhat high, which my wife, who was checking in on me, didn't fail to point out. Additionally, I now was also the lucky recipient of a check engine light! I ran the codes and got a misfire on cylinder 3. Changed the coil again on that cylinder to no avail. Luckily, I had mistakenly ordered seven instead of six spark plugs which allowed me to remove the plug from this cylinder and put in the spare. This fixed everything! Well mostly, because now dear wifey suggested that we try the new coils one more time. So I pull the old ones, really jam in the new ones, start the engine again and guess what? It DOES NOT START! So I reinstalled the old ignition coils one last time resulting in an immediate engine start and a smooth idle! Now all I have left to do is return the darn new coils. However, I am baffled as to why they utterly failed. They are the same brand, look identical and come from a reputable source. Also, I made sure (twice) that the wire plugs clicked in place and the coils were firmly seated in their spots. Oh well, you live and learn, but I would really like to learn why they didn't work!

[bluewater328]

I think the Delphi ones are the new default plug in case that issue rears its head again. Might want to try those.

[BMWinAZ]

Originally Posted by bluewater328

I think the Delphi ones are the new default plug in case that issue rears its head again. Might want to try those.

Thanks for the tip. That was my thought also, in case one of the old coils should eventually go bad. Either Delphi or Eldor.