BMW Ignition Coil Problems
When I first started as a BMW tech, there were pretty much two engines out there in practically every car, except the M cars, of course. There was the N62 and the M54. So many cars with the same engines. This is how we get so good at fixing them. It's the same problems in most of the cars so we know what to look for and what we need to do to fix it. Anyway, one of the big problems that these M54 engines had was the ignition coils. They used to fail all the time, and at one point BMW had a huge recall (about 500k cars) to replace all the coils on the 6 cylinder engines. If they weren't replaced they would swell up, short out internally and damage the DME (engine computer).
Here are two views of a typical BMW ignition coil. This is what makes the spark plugs fire. There are not spark plug wires. The DME controls these directly, and since each spark plug gets a whole coil all to itself, it can fire the spark plugs more effectively.
The only bad thing is that more than a decade later, these are still going bad all the time. The N51, N52, N52TU (basically the same engine) all use these coils, and for some reason they fail. Now for some very weird reason, the same coil in an N54 or N63 does not fail. Maybe because of the increased torque, somehow it causes less stress on them. One thing's for sure, when they go bad you'll feel it. They can fail completely, in which case the engine will feel like it's hopping inside the engine bay. Or they can fail under a load, which means when you're doing hard acceleration or trying to accelerate at a high speed (45-50 mph) on top gear. At this point you'll feel the engine feel like it's intermittently bumping/ stopping for a split second.
To make a long story short, these coils fail so much that BMW recently published a service bulletin saying that under certain circumstances, if a car comes in with a bad coil, we now need to replace all 6 coils, not just the one that failed, with an improved coil made by delphi. They are very easy to replace, by the way.
Looking for some advice..I have a 2011 BMW, that is "failing under load" exactly how you have described. I have an extended warranty that will only cover this if they fail completely "throwing hard faults" - I think this is ridiculous. I don't feel safe getting onto a highway as I feel like I may get hit from behind when the car bucks. Is it possible that the coils can be bad and the computer just isn't showing it? And how can I get a copy of this service bulletin? Thanks so much!
ReplyDeleteThe sib is 12 18 14. Unfortunately I cannot post the sib here. What engine does the car have and how many miles are on it? You can definitely have a bad coil and not have the computer register it. The engine computer detects a slow down of the rpms through the crankshaft sensor when the misfire happens, so if it only misses sporadically it is hard for the computer to determine which coil is missing. Unless it misses many times in a row, it wont set a light. I completely understand about the extended warranty. We fight with them all the time, and a lot of these times, that's just the way they work. They usually cover failed components. Any good shop can figure out which cylinder is missing, though. We know how to load the engine so it misses many times in a row, or swap the coils until the missing stops, and then they can go claim it through the extended warranty. If it currently misses under load, they should be able to figure it out.
ReplyDeleteMy x6 with the N63 engine is as described, stuttudering under load when accelerating in high gear. And it seems like it happens on majority of the first year production n63. Replacing the ignition coil solved the problem.
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