1933 Geo Prizm Lurches Upon Acceleration


Does anyone have a clue as to why my 1993 Geo Prizm, LSi w/1.8-liter engine & manual transmission lurches when I accelerate and is more pronounced when the engine is cold?

The troubleshooting steps to date:

*Cleaning fuel system & injector.

*Changing the spark plugs.

*Recently had distributor timed due to smog check inspection.

Any suggestions?