I HAVE A 2001 WINDSTAR 90000MILES THE CHECK ENGINE HAS BEEN ON FOR AWILE I JUST DROVE IT AND I HAVE BIG PROBLEMS its spitting and lose of power and you can hear a vacum leak when you give it the gas at the back at the intake and a knocking noise in the intake please help thanks jim

While it is located at the front of the engine, a common vac leak is the
"U" shaped vac line that runs from the fuel pressure regulator to the upper
intake manifold. Space is pretty tight behind the engine. Removing the
cowl will give you access to look for leaks. The knock could be a loose baffle in the upper intake, there are posts on repairing. If the upper intake gasket/
isolator bolt repair hasn't been performed yet, this could also be the source of your vac leak, yours sounds more severe though.

Check the post at the top of the windstar room, it has LOTS on information, including a link to a site that is just great in explaining and showing what is involved.