Cladman

Cruising at 120km/h and 2000 rpm (At highway speed with no load) the rpm will fluctuate 200 rpm. This will last 10-20 seconds. When I push the throttle there is no hesitation (premium fuel) with 120000km on the RDX. Haven’t approached the dealer with my concerns since I’ve had the Rdx there for a P3400(VPS stuck off bank 1) Feb. of this year. This being the only work done outside of maintenance to our vehicle.

egads

Probably VCM kicking on/off. Muzzling is an available solution.

Maverick91

My 14 RDX was surging at highway speeds or during general acceleration. Per other post here on the forum I had Rear Differential Fluid, Transfer Case Fluid, and Transmission Fluid changed. Problem went away! Mine needed done around 45k miles.

egads

At 120,000kn, you should have had at least two trans fluid changes by now. If you have the AWD version, then the fluids related to that as well.
Do check out the service bulletins related to your model year (that you did not disclose) up in the stickies.

Here is the second one related to a software update on the transmission:

http://www.urvi.net/forumfiles/SB/B17-018.PDF

ronsteve2112

My 2015 has done that ever since I have had it. Bought it with 39K and the 30K tranny change under its belt, and I had it done again at 60K. I'm thinking it's VCM, but the only thing I'm certain of is that it's annoying.

egads

Then Muzzle the VCM. That "feature" does not save a significant amount of fuel. It only helped Honda achieve better corp average fuel economy ratings.

These are the two best units:

https://www.svcmcontroller.com

https://www.vcmtuner.com/products/vc...e-vcm-eco-mode

Keep in mind that these folks making and selling these things can lay it on a little thick with their explanations of how and why it is important to do this.
Honda did use some experimental low friction piston rings in some models using this v-6 engine. The VCM in those vehicles were and are a disaster.
The Acuras never used those rings and have much better engine mounts to boot. But it is so much nicer to have all 6 cylinders all the time. If one is going to keep
the car long term, I think I would highly recommend doing what you can to keep all cylinders running.

Cladman

Flushed the tranny, front and rear diff and the issue went away.

tinmaner

just curious
is using the svcm is same as driving the car in sports mode all the time ? or is it different ?

egads

I think the sport mode just changes the shift points in the transmission.

tinmaner

hmmm it also doesnt let the 3 cylinders die as opposed to the regular mode .. no ?

egads

If you had intended to communicate something with that sentence, it did not work.

tinmaner

lol sorry
what i meant was

when in sports mode does it still kill the 3 cylinders like it does in economy mode ?

egads

Yes, VCM is still active in sport mode. Probably not as active in stop and go traffic, but will still happen once up to speed and you level off the throttle.

meburdick

I'm experiencing this same sort of thing.

2017, AWD, 35k miles. Bought it CPO with about 22k on it and don't recall this happening originally. That doesn't mean that it wasn't, just that we didn't notice it. 93 Octane High Detergent gasoline pretty much exclusively (there have been occasions where 93 was used that WASN'T High Detergent).

Rear diff was flushed at roughly 30k along with engine oil and filter, getting ready for the tranny drain and fill as well. Since it only seems to do it when traveling at least 35-40MPH and on either a steady grade or slight incline, my expectation was that this was the fuel management / cylinder deactivation controls at work. Annoying, to say the least.

If a transmission fluid service makes zero difference, then the cylinder deactivation controls are going to get shut down.

meburdick

Update... Had the transmission fluid drained and refilled twice (drain / fill, drive about 150 miles, second drain / fill). After the first iteration, the issue was probably 99% resolved. After the second iteration, it's completely gone. Car had 41k miles at the time the transmission fluid was changed. Rear Differential fluid had been changed at 30k and the problem started around 33k-35k. So, it's not at all related to the rear diff fluid and seems to be completely tied to the transmission fluid.

For reference, I bought a dozen quarts of Honda ATF off of Amazon for about $100 (eight have now been used) and paid a mechanic $200 to do the two visits for me as I didn't have the time or the space to do the work this time around.

egads

I would still recommend getting the transmission software updated.