I'm afraid I have no good tidings today. Let me get straight to the meat of the story.
Last Sunday, I left the house in the Z3 with the usual EV grin on my face. A few houses down I noticed a slight vibration through my hand resting on the gear shift. I thought "Hang on, I don't remember this." But it was slight and I hoped it was my imagination. Well over the next few days I realized that not only was it NOT my imagination, but it was getting steadily worse.
Of course, I immediately went into trouble shooting mode. Ultimately I was stopped on the side of the road, with the car in neutral, carefully revving the motor. Sure enough, the vibration started up at about 2000 RPM. It was worse at about 2500 RPM, and then seemed to start abating, but it did not go away entirely. Since I was sitting still, that rules out the possibility that the imbalance lies in the transmission or beyond in the drive line or wheels. It is in the motor and clutch assembly.
I pushed the clutch in, held it and revved again, same thing. That test ruled out the clutch disk since it wasn't spinning with the motor at that point. The vibration was still present. That leads to the following conclusion. One of the following things has managed to fall out of balance: the motor, the flywheel or the clutch plate.
I find it hard to believe that a solid hunk of aluminum has somehow gone out of balance, so I think it's safe to rule out the flywheel. That leaves the motor or the clutch plate. Unfortunately, each of those seems as unlikely as the next, but there's no getting around the fact that one of them has gone out of balance.
So, what next? Well, I can't leave it this way. I noticed it getting worse in only 4 days and about 100 miles. There's no way it's going away. It will only get worse, do more damage and get more costly to fix. I'm going to have to pull the motor and transmission assembly, dis-assemble it and find out who the culprit is.
So there you have it. Hopefully I won't be out of commission too long. I had to drive my old ICE Passat this past weekend. I definitely miss the EV grin. Please feel free to leave your condolences.