Diagnostic guidance. Suggested checks and possible repairs are separate from the owner's reported results.
Provide any findings from the planned return visit to the dealer and clarify whether the engine restarted immediately after the reported stalls.
Source: Original question and visible replies. Owner reports and other participants' experiences are distinguished. Next steps are editorial requests for clarification or existing diagnostic findings, not a verified repair procedure or an independently confirmed component diagnosis.
2003 Mustang Mach1 Stalls
The owner of a 2003 Ford Mustang Mach 1 reported repeated stalling. A dealership replaced the idle air control valve, followed by a period without stalls. The problem then returned five times in one day, when releasing the accelerator or coming to a stop.
Reported outcome: The initial improvement after valve replacement did not last. No lasting repair was reported.
A reply suggested the fuel filter, but the owner had not checked it. The planned dealer visit is not evidence of a completed diagnosis or repair.
