sjsa

I purchased my RDX Adv 3 weeks ago.
I noticed RPM goes higher above 4000 when I drive downhill without applying accelerator pedal.
It seems the gear doesn't shift properly on downhill so it causes RPM goes up.

JB in AZ

If you are using cruise control, and the car is inclined (no pun intended) to speed up on the down hill, the transmission will shift to a lower gear to try to maintain the preset speed, causing the RPMs to go up. Perfectly normal.

sjsa

I don't use cruise control.

RDX-Rick

You didn't mention if you were driving with cruise control turned on or off!

Without cruise control, the vehicle will speed up when going down the hill, and the RPM will also increase with your foot off the accelerator, however RPM will not rise suddenly or drastically.

If cruise control is on, the car will maintain it's speed (within reason) and the transmission will downshift to provide engine braking. When downshifting occurs, the RPM will increase suddenly, and often drastically, like a jump from 2000 RPM to 4000 RPM.

So either way, it is normal for the RPM to go up, when driving down a grade. Since you mention an RPM of 4000, I suspect you have cruise control turned on.

Perhaps you haven't had a new car for several years. In the past, cruise control systems, only controlled the throttle, and had no control over the brakes and transmission. These older cars would simply allow the throttle to close (same thing as taking your foot off the pedal) and the car would gain speed going down a hill.

If you could be more specific in describing the circumstances under which you notice this, and what you expect would be normal when going down a hill, you may get a better explanation.

97ws6

Make sure you're in D Drive and not S mode. The transmission goes in to S mode if you press the D twice.