Possible bad motor mount
There are many possibilities: Bad motor mount Weak spark low fuel pressure Has anyone done maintenance/repairs??? If you open hood and power brake car in drive and reverse you can see the engine jump if you have a bad motor mount
Vibrations,
The car needs a tune-up, or the motor mount(s) are bad.
It is a honda van! Well that dependes on what car you have and which motor mount is bad
Possibly a bad motor mount
Could have a bad motor mount
I have a motor mount going bad. When I shift from park into drive sometimes I hear this THUMP and it is LOUD. That is tell-tale sign of the motor mount being bad. It is the engine shifting because there is no mount to hold it in place. It's really loud like WHUMP!!!! :-) As far as I know, this is not something u want to let go too long as it can be very dangerous should the other side of the mount break too.
This you could get away with for awhile without further damage. Motor mounts have a built in safety device to keep the engine in place when the rubber mount breaks.
When you have a bad motor mount you may feel a thud when you try to change the gears of your car. You may also find that your motor moves a little because it isn't secured to the car properly.
the motor mount is bad
Can be many things. Broken motor mount, bad universal joint in the drive shaft, transmission problem, oil on clutch if it is a manual trans, vacuum leak, to name a few.