[mazza2590]

Hi Everyone
this is my first post, so please let me know if Im doing this wrong!

tl;dr - engine light came on after a few weeks of weird noises and engine knocking. Ended up with 4 dead coils and getting all 6 + plugs replaced under CPO warranty. But why now?

Let me preface by saying that I still have a lot to learn about BMW.

Now that I got that out of the way, let me explain what happened.

I've owned my 2011 E90 - 328i xDrive for about 1.5 years now. Purchased it from a dealer as a CPO at about 47,000km. It now sits at about 77,000km.

I've never really had any major issues with it, but it did feel a bit "weird" for a while. I live in Toronto, so the winters get pretty cold. When I first start the car in the morning, I realized that it would get really jerky if I don't let it warm up.For example, When I reverse out of my driveway 5 seconds after I turn it on, it would often jerk / accelerate backwards. RPM gauge would go from 1,000 to 2,000 without me touching the pedals. That is really scary to me! I've asked my adviser at the dealership about it and we never really found a cause for it. I've avoided this issue by simply letting it warm up for 30 seconds or more and its fine. But still worrisome.

Fast forward to about 3 weeks ago where I started hearing an odd sound from the engine. It seemed as the drive belt or one of the belts was much louder than usual. I pulled over to check, but was not able to see anything noticeable.

This issue got much worse on Friday as I was driving to work. As I was accelerating on the highway, I felt the car jerk forward. As if I had a bad gear change, or something similar. It happened about once or twice, and so I was moderately concerned. On the way to my girlfriend’s house after work, it happened about 5 times, so now I’m getting very concerned and told myself that I will take it to the dealer on Saturday.
Friday night when I was ready to go home, I got about 300m from her house before the engine light came on and the engine started shaking very violently. I immediately stopped the car and went back to her place. In the morning I got it towed with a flatbed.

Today my adviser from the dealership told me that through their tests, they found that they needed to replace all 6 coils and all 6 spark plugs. Luckily this was all covered via my CPO warranty, so I’m not out any money, but I’m curious to know what the heck happened.
On the actual work order it says that Coils 1, 3, 5 and 6 were 100% dead. So had I not been under warranty, I’m sure I could have gotten away with just replacing those 4. But because I was covered, and I guess the remaining coils and plugs were reasonably bad enough, I was able to get it all replaced

My question is, is my "cold jerky" issues related? Have my coils and plugs been bad for a really long time? Or did all 4 just become faulty all at once?

Thoughts?



The notes from the work order is here:

View post on imgur.com

[robthewrench]

The coils are most likely the source of your jerkiness. After reading the work diagnostic notes, it seems like the tech did a thorough check-out and started with a compression test.

Coils do go bad over time. The heat cycling of the coil affects the insulation within the coil and after enough heat cycles the coils will develop an internal short and not produce the voltage required. While the tech said 4 coils were completely dead, this may be a stretching the truth a bit. I would guess that at least one coil went completely bad (shorted out) and this caused the violent shake and check engine light. The other 3-5 coils probably did not test out well and showed greatly reduced performance.

[kkasson]

It also says that they adjusted the cam timing? That's odd...these cars typically never have timing issues. The timing chain won't skip a tooth the way that timing belts sometimes can. Since the compression and leak down tests were fine there isn't any damage caused by it, so I wouldn't worry about it. But that could definitely be a cause of the jerkiness.

Like he said above, the coils do go out on their own. 77,000km is a bit early for them to wear out, but it is what it is. But I'd bet that the timing was also a big part of the problem.

[mazza2590]

Originally Posted by robthewrench

The coils are most likely the source of your jerkiness. After reading the work diagnostic notes, it seems like the tech did a thorough check-out and started with a compression test.

Coils do go bad over time. The heat cycling of the coil affects the insulation within the coil and after enough heat cycles the coils will develop an internal short and not produce the voltage required. While the tech said 4 coils were completely dead, this may be a stretching the truth a bit. I would guess that at least one coil went completely bad (shorted out) and this caused the violent shake and check engine light. The other 3-5 coils probably did not test out well and showed greatly reduced performance.

Originally Posted by kkasson

It also says that they adjusted the cam timing? That's odd...these cars typically never have timing issues. The timing chain won't skip a tooth the way that timing belts sometimes can. Since the compression and leak down tests were fine there isn't any damage caused by it, so I wouldn't worry about it. But that could definitely be a cause of the jerkiness.

Like he said above, the coils do go out on their own. 77,000km is a bit early for them to wear out, but it is what it is. But I'd bet that the timing was also a big part of the problem.

Thank you for the replies!
very much appreciated.