Shuttering drivetrain

[davideos]

Something interesting happened today. While pulling into my garage, I experienced a *shuttering* affect; for lack of a better term. It was as if I was tapping the brakes at about 3-4 times a second. My driveway is at a slight incline. I backed out and even going backwards with the car in reverse, it did the same thing. So I went back and forth a few times and it seemed consistent.

I took the car back on the road, and it seemed fine going at normal speed, but if I slowed down to a near stop, it would do it again, and if I accellerated very slightly...basically idling without putting my foot on the accellerator, it would also do it (at any include). I went to a street in my neighborhood with a slight incline and let the car come to a crawl while going uphill. As it got to nearly a stop, it would start to shutter again. This went on for quite awhile. I eventually put the car in neutral to see what would happen if I let it slide backward downhill while I applied or not applied the brakes. I wanted to see if it was the brakes or the motor. It was then that the car snapped out of it.

I've never experienced this before. I believe the problem was with the car's hill assist in some way. Anyway, something to look out for.

 

[WattsUp]

I've never experienced this before. I believe the problem was with the car's hill assist in some way. Anyway, something to look out for.

I think I've felt what you're describing.

However, I never thought it was the brakes. Rather, I just thought it was a phenomenon deriving from how an AC electric motor is driven using multiple magnetic fields, creating a "pulse-like" effect at very low speeds.

That said, most of the time, I don't perceive the pulsation. My conclusion is that sometimes the car does it, sometimes not, maybe depending on conditions -- or perhaps sometimes I notice it, sometimes I don't.

 

[hybridbear]

Something interesting happened today. While pulling into my garage, I experienced a *shuttering* affect; for lack of a better term. It was as if I was tapping the brakes at about 3-4 times a second. My driveway is at a slight incline. I backed out and even going backwards with the car in reverse, it did the same thing. So I went back and forth a few times and it seemed consistent.

I took the car back on the road, and it seemed fine going at normal speed, but if I slowed down to a near stop, it would do it again, and if I accellerated very slightly...basically idling without putting my foot on the accellerator, it would also do it (at any include). I went to a street in my neighborhood with a slight incline and let the car come to a crawl while going uphill. As it got to nearly a stop, it would start to shutter again. This went on for quite awhile. I eventually put the car in neutral to see what would happen if I let it slide backward downhill while I applied or not applied the brakes. I wanted to see if it was the brakes or the motor. It was then that the car snapped out of it.

I've never experienced this before. I believe the problem was with the car's hill assist in some way. Anyway, something to look out for.

I've had this happen a number of times. Every time it has been after driving many miles on one charge (50+). It has not happened since temps turned cold. There is a TSB that addressed delayed reverse engagement which we also experience almost daily. Sometime in the next few months I'll take the car in for that TSB and I hope this issue goes away as well.

I've found that the shuddering continues even after turning the car off & back on. Sometimes we could drive many trips with it shuddering at every stop even with multiple times turning the car off & on. Every time it has happened the car has then sat overnight to charge and the shuddering has gone away by the morning.

Edit: Here is the TSB for the reverse engagement.

 

[WattsUp]

I think the "shuddering" davideos is described is probably markedly different from the prolonged gripping of the brakes covered by the mentioned TSB.

 

[hybridbear]

I think the "shuddering" davideos is described is probably markedly different from the prolonged gripping of the brakes covered by the mentioned TSB.

I agree. And we experience both concerns. But my thought was that perhaps the software update called for under the TSB will also address the software issue causing the shuddering. It feels like the electric motor is trying to creep & fighting the brake pads when it happens.

 

[WattsUp]

... my thought was that perhaps the software update called for under the TSB will also address the software issue causing the shuddering. It feels like the electric motor is trying to creep & fighting the brake pads when it happens.

Yeah, possibly. Just didn't want to give davidos false hope that there is a TSB covering his exact issue.

I actually think the shuddering I described is probably something "normal", and just a phenomenon of AC motors.

 

[davideos]

From what hybridbear described, I think this is the same issue. This is the first time I experienced it. I don't think it is the AC motor. When it was occurring in my driveway/garage, I rolled the windows down so I could hear better. I could definitely hear a mechanical noise in sync with the pulsing / shuttering. It may not be the brakes, but I highly suspect that it is.

Anyway, it went away when I put the car into neutral and let the car back out the driveway under the power of gravity. It didn't go away instantaneously, but rather faded away shortly after I started to roll backwards while lightly applying the brakes.

Another thought on the matter...when the car slows under regen braking to a certain point, it stops regenerating and applies the mechanical brakes. The issue might be more related to this function as hybridbear and I noticed this when coming to a stop. Although I mentioned that I experienced this with my foot off of the brake and idling (slight electric propulsion), I was going uphill, which was actually slowing the car. The slower the car went, the more shuttering occurred.

As I said, it is gone away now. I'll keep my eye on it. This is the first time it occurred in the 2 years I've owned the car. I won't bother taking it to the dealer unless I can reproduce the issue.

 

[dmen]

I experienced something like this once a few months ago. Driving home from work (~85% battery, no charging at work), every time I came close to a stop, or crept in traffic, the car moved jerkily rather than smoothly. It wasn't dramatic, but different enough to notice. Had nothing to do with inclines, as there are none here. Driving above like 5 mph was normal. Anyway at some point at a stoplight, I moved the drive selector to park and back to D, and it started behaving normally again. It hasn't happened before or since. If anyone else sees anything like this, see if shifting to neutral/park and back, or powering down and back on, solves the problem.