Has anyone who brought their V6 TLX to the shop to have the highway-speed vibration fixed had anything done to the Active Control engine mounts? I was browsing the Power Train section of the 2018 TLX Honda Press Kit and read the following:
" V6 Active Control Engine Mounts and Active Sound Control
A powerful 28-volt Active Control Engine Mount system (ACM) is used to minimize the effects of engine vibration as the VCM system switches cylinders on and off. Sensors alert the Electronic Control Unit (ECU) to direct ACM actuators positioned at the front and rear of the engine to cancel engine vibration using a reverse-phase motion. In the cabin of the TLX, an Active Sound Control (ASC) system further mitigates low frequency noise that can occur during 3-cylinder operation. "
I now wonder if the programming of the reverse-phase motion could be the culprit. Maybe other harmonics or influences not experienced during R&D are at play in the real world.
In my experience, when it happens, the vibration does not always occur with the same intensity, although I am traveling at the same speeds on the same roads. Interestingly, the frequency of the vibration does not change in sync with the wheel speed, but more slowly. It seems to be linked to the engine speed, which in any of the overdrive gears, 5th through 9th, a smaller relative change in engine speed would be expected with a greater change in wheel speed.
Replacing tires, either with the same brand or a different brand, tire pressure adjustments, road force balancing and even changing transaxle mount and rear subframe bushings haven't completely cured what is ailing us.

Has any service representative, technologist or Honda engineer examined the engine mount system as a possible cause of the vibration? If not, perhaps anyone who has been pursuing this issue, having had other attempted remedies fail, should consider bringing this possibility to the attention of Honda.

 

So after I had my transmission replaced, all of a sudden whenever the car dropped to low RPMs and especially when the automatic cylinder stop kicked in like at 70 mph, I would get this huge vibration like the engine was lugging. Turns out the active engine mounts had to be "synchronized" with the car in gear, according to techline. This corrected the problem and now the car is smooth as butter again.

 

Thanks for the post, maybe synchronizing the mounts could help all of us with this issue.

 

Two questions comes up in this scenario:
1) Was the sync not properly done at factory?
2) Will the sync get lost over the long run, and then becomes a occasional thing to "fix"?