Ford Mustang 1989-1993 Repair Guide

PCV Valve System



The PCV valve system vents crankcase gases into the engine air intake where they are burned with the fuel and air mixture. The PCV valve system keeps pollutants from being released into the atmosphere, and also helps to keep the engine oil clean, by ridding the crankcase of moisture and corrosive fumes. The PCV valve system consists of the PCV valve, it's mounting grommet, the nipple in the air intake and the connecting hoses. On some engine applications, the PCV valve system is connected with the evaporative emission system.


See Figures 1, 2, 3 and 4

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Fig. Fig. 1: PCV system-2.3L (VIN A) Engine

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Fig. Fig. 2: PCV system-2.3L (VIN M) engine

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Fig. Fig. 3: PCV system-5.0L engine

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Fig. Fig. 4: This is where the crankcase vapors are drawn from the engine-5.0L engine

The PCV valve controls the amount of vapors pulled into the intake manifold from the crankcase and acts as a check valve by preventing air flow from entering the crankcase in the opposite direction. The PCV valve also prevents combustion backfiring from entering the crankcase in order to prevent detonation of the accumulated crankcase gases.


  1. Remove the PCV valve from the valve cover grommet. On the 5.0L engine, the PCV valve is located on top of the block by the firewall, while the 2.3L engines is mounted inline with the breather hose.
  3. Shake the PCV valve. If the valve rattles when shaken, reinstall and proceed to Step 3. If the valve does not rattle, it is sticking and must be replaced.
  5. Start the engine and bring it to normal operating temperature.
  7. Disconnect the hose from the remote air cleaner or air outlet tube, the tube connecting the mass air flow meter and throttle body.
  9. Place a stiff piece of paper over the hose end and wait 1 minute.
  11. If vacuum holds the paper in place, the system is okay; reconnect the hose.
  13. If the paper is not held in place, check for loose hose connections, vacuum leaks or blockage. Correct as necessary.


  1. Disconnect the vacuum hose from the PCV valve.
  3. Remove the PCV valve from it's mounting grommet.
  5. Installation is the reverse of the removal procedure.