I experimented another solution that makes the Touchpad of the HP Pavilion dm4-1160 less erratic. It uses the program synclient (in command line) to modify on the fly the parameters of the synaptics driver.
In the console, type this command:
synclient MinSpeed=0.1 MaxSpeed=1 AccelFactor=1 JumpyCursorThreshold=60
You can type sysclient -l to check the parameters in use.
The parameter to calm down the pointer is JumpyCursorThreshold=x; lower is the value x and more lazy the touchpad will be! I found the good value is around 50 and 100. You can enter the new value with synclient and immediatly check the result.
This solution is not perfect, for instance, it's not possible to click with one finger and to move the second finder to resize a window. The other problem is synclient doesn't save the parameters. So, you will have to redo it at the next boot. I will explain how to modify the configuration file.