Intake Manifold Cleaning Caution (#1)
This solution covers Ford 4.6L VIN 'W' Engines (1991-'98).
If piston failure occurs in this engine, it is possible for broken pieces of piston to end up in the intake plenum. This is due to the design of the engine, which has tuned runners with the plenum located below the runners.
The piston pieces may be ingested into the engine if they aren't removed during cleaning. Failure may not occur immediately, as it may take wide open throttle operation to create enough turbulence to ingest the pieces.
To properly clean this manifold requires removal of at least one of the large core plugs from the bottom of the manifold. This cleaning process must be properly and thoroughly performed to avoid catastrophic engine failure.
Competition Engines, Eagen, MN