We just completed a 1200 mile road trip, and the RDX was a dream to drive except for an occasional vibration in the floor. At cruising speed (70-75), everything was smooth. But we noticed that when accelerating, we could feel and hear a vibration under our feet. It tended to be more noticeable after running for a couple of hours. If we stopped at a rest area for a while, when continuing we wouldn't notice it at first. I'm due for my first maintenance visit, but any ideas? We were running with 93 octane the whole trip.

My wife did say, however, that she thought I was nuts for getting this car, but after the trip, she now gets it. She actually switched into sport mode on a winding section of highway in the mountains of Virginia.

 

Do you feel the vibration in the steering wheel? I'd suspect a defective tire until proven otherwise.

Could be a driveshaft problem, if it's SH-AWD, but not likely.

The other thing "under your feet" is the exhaust. 2019 RDX does have quite a rumble when you accelerate at low rpm. Dunno why that would be louder and/or you would notice it more after cruising for a while.

Engine mounts are another possibility, but it's even harder to explain why that would change.

 

No, the steering wheel is fine, and I had a road force balance done back in August. It is SH-AWD, and that and the exhaust were my first thoughts, especially since it seems to happen after it has time to heat up.

 

I'd rotate tires front/back and recheck. It might not be the problem, but that's a heck of a lot cheaper and easier than next steps. I've had defective Conti tires that were out-of-round, same model as we have on 2019 RDX. IIRC the vibration got worse on long trips, which made me a bit nervous, to say the least. Apparently internal tire defects can manifest more strongly when the tire is warm.

 

Did you happen to notice the RPM's? Are you sure it was from under the floor and not the engine? See this post:

https://acurazine.com/forums/third-g...umming-973470/

 

I did not notice the RPMs, but the sound could be described as a humming, but when I was the passenger I definitely felt a vibration in the floor. Thanks for the link, I had not seen this post, but it does sound close to what I experienced. So I'm sure the answer from Acura is going to be "it's a characteristic of the vehicle".

 

any chance it is from underneath your seats?

 

Are you thinking seat ventilation fans? It's not an unreasonable suggestion, if the vehicle is so equipped. Centrifugal fans can generate more vibration and/or noise when they are subjected to external acceleration, especially if the force causes the "squirrel cage" to come in contact with something. Same with the main cabin HVAC blower.

 

 

And your feet were in the footwell, up under the passenger dash by the firewall?

I'm wondering about the rear engine mount. Are the engine mounts in this vehicle the fancy electromagnetic vibrating kind, that are intended to counteract engine vibration? I know they are in 3rd-gen MDX and Pilot, but those have cylinder shutdown.

But I haven't ruled out drivetrain noise/vibration. IIRC this vehicle has three driveshafts; two short ones up front and then a long one to the rear diff. Supposedly that enables them to mount the engine/transaxle lower in the engine bay, to lower the center of gravity and improve cornering.