P0171 Ford - on a 1995 Mercury Grand Marquis

Question

Car doesn't stay running on start up when cold. Or will run rough.

Answer 1

P0171 Fuel trim lean

This is a vacuum leak, check for vacuum leaks especially at the PCV hoses or any vacuum hose that may have ruptured to cause the vacuum leak , what vacuum leaks are is air that gets past the MAF (mass air flow ) sensor