Mechanics stumped with vehicle shudder & dies, no check engine light or codes on 2004 Ford Freestar

Van dies sometimes & shudders while driving. The fuel filter, spark plugs & plug wires have all been replaced. Any thoughts of what to check? The check engine light has never come on & there have never been any codes either.

Asked by for the 2004 Ford Freestar
Could be intermittent ignition switch failure
Thanks. After doing some extensive online research, there was a TSB to fix this issue. Apparently water gets into the PCM.