I know a lot of other people have asked this question, but I'm asking it again because I've replaced many of the suggested problematic sensors, parts... and am still having the issue.
Timing belt replaced at 88,000 miles ( currently at 119,000).
Ignition coils and spark plugs and valve cover gasket replaced and fuel injectors cleaned in October 2011.
January 2015, the crank and cam position sensors "shorted" and were replaced.
What's left? Because the issues have not stopped. At this point, dealer is telling me they find nothing, no codes, no check engine light... and they can never get it to do it when they have it. HELP!
Thanks.

When did the problem start? If you disturb old spark plug wires, you can, sometimes, cause all sorts of weird performance issues with a car. How long has it been since you replaced the spark plug wire set? I recommend doing it at 100,000 miles. Another problematic component is the MAF Sensor, which can definitely cause jerking and stalling issues. If you decide to replace it, my advice is to go OEM. You may want to put an advanced scan tool on the car and check for pending codes. Don't overlook, either, your transmission. Check the fluid level, when the transmission is at normal operating temperature, the engine is running, and the shift lever has moved through PRNDL. Make sure the fluid is pink, not brown or black, and that it doesn't smell burnt.

What brand of plugs did you install? Check for spark at each plug. Remove the plugs and see if any of them tell a story.