Fuel injectors can short-circuit electrically causing a rougher than normal idle and reduced performance.Google+
Car Problem Reports
Pontiac Grand Am Fuel injectors can short-circuit
Pontiac Grand Am Problem
Engines Affected: 3.3L V6, 3.4L V6
Visitor, 2005 Pontiac Grand Am, 3.4L V6, 86,000 mi
running rough at idle 204 error code replaced injector was fine for 20-30 miles then repeated 204 error code exchanged injector same thing. found a short in the injector harness.