my 94 LS400 jerks intermittently and w/o warning.I cleaned the throttle body and replaced fuel filter?

Answer 1

There are many causes for this behavior. It can be generated by the PCM, or it can be the result of poor information collected by the PCM, or a command poorly communicated by the PCM, or even fuel related. But to know what to do you need to begin with diagnostics.
Go here----->

http://autorepair.about.com/library/ts/obd-i/bl-dtcs-65a.htm

...and scroll down below the code descriptions and follow the procedure for retrieving the codes.
Use the descriptions to guide you to the correct circuit or system to begin the diagnostics, and the repairs necessary.
NOTE-----> The codes refer to a fault or failure in a system or circuit, and DO NOT necessarily refer to a failed component.
It is best to either purchase a repair manual, or go to the library in the REFERENCE section and use the manuals there for guidance and repair procedures.
OR... you can go here------->

http://www.eautorepair.net/

...and for an annual subscription fee you have access to all of the published professional diagnostic, repair, diagram, illustration and recall information available for your car. Very good stuff.

Good Luck