It only pulses when it comes out of the diode. This is known as "ripple" but a properly designed rectifier will use an inductive choke to damp this out and leave virtually no ripple in the final output.
Most of the electrical pulsing that an automobile puts out comes from the points in the distributor, which are often poorly filtered. This can be bad if you are powering a RF transmitter directly from the electrical system and usually requires a choke between the battery and the transmitter. It's often a problem for Hams when they install a mobile transceiver.
Points...distributor....wow, haven't heard those terms for awhile. Just how old is your vehicle?