To clarify, the technician working on Joe's 1997 F150 is more than knowledgeable & qualified to diagnose his vehicle's concern. The challenge was when he dropped off vehicle it was not exhibiting the driveability symptom Joe described. Technician connected test equipment & road tested to gather data and returned to shop to analyze. Spark & fuel control systems were tested, were normal. Mass air flow sensor tested fine. 1 spark plug was removed/inspected, was fine, no evidence of misfire. Performed fault code test, none in system although Joe said a code P0455 was erased from system. Tech performed evaporative emission system (smoke/leak) test and found a large vacuum leak at the fuel filler neck area. All (above) findings were discussed with Joe and he declined further inspections/tests.
Joe initially authorized $120-$240 to diagnose the concern. His bill was $143.88 +tax. The "$10 part" he mentioned was for shop supplies (cleaners/diag material/software costs) as is typical for this type of concern. No "parts" were charged.
the common maintenance tasks to this business. Take it to a dealer if its a big price repair item.