I have a Mazda 2021 CX9 GT SP with 20,000KM (12400Miles) which I bought brand new and service with Mazda.

I would appreciate if anyone can shed some light on a problem which is hard to reproduce and very hard to describe

If I am driving towards say red lights and I take my foot off the gas and let the car roll to a stop with very gentle braking, as the car comes to a complete stop (with my foot on the brake) the drivetrain starts to pulse forward.
At this point the engine is still running and the Stop/start system has not kicked in even though it is activate. Also, the engine is not revving , its just on idle

The sensation is like someone is behind the car pushing it, stopping, then pushing it harder, then stopping , the pushing it even harder.

To get the car out of this loop I need to either take off and start driving or turn off the engine and turn it back on.
If I put the car into park and back into drive , it starts doing the same thing again.

To me it feels like the engine is applying torque on the transmission, then letting go, then applying torque again but with more force, then letting go and repeating this with every application of force getting more powerful, but the engine is not revving.

Needless to say my local Mazda dealer had no idea what this is and I cannot reproduce it at will so had no way of showing them.

cheers

 

It is a help if you put your location and your car's model-year into your profile.

Do you see this pulsing on your tachometer? If you take a video of this you'll have something concrete to show to the service writer. Or is there any other way you can capture this on video, sound included? (could it be a transmission problem?)

 

Its a 2021 model in Australia. There is no noise or tachometer movement as it only happens on idle. Its a feeling of the drivetrain pulsing forward in a positive feedback loop that gets more powerful that the driver and passengers can feel.
I'll try to capture it on video,, but its so far I cant reproduce it at will