Honda Accord/Prelude 1984-1995 Repair Guide

Positive Crankcase Ventilation (PCV) System

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OPERATION



See Figures 1, 2 and 3

All Honda vehicles covered by this information utilize a closed positive crankcase ventilation system. This system cycles unburned fuel vapors (which work their way past the piston rings) back into the intake manifold for reburning with the air/fuel mixture. The oil filler cap is sealed; the air is drawn from the top of the crankcase into the intake manifold through a valve with a variable orifice. This valve is commonly known as the PCV valve.



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Fig. Fig. 1: PCV system flow-1988-91 fuel injected Preludes



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Fig. Fig. 2: PCV system flow-1986-89 Accords

The recirculation system relies on the integrity of the engine seals. Any air leak around a valve cover, head gasket, oil pan, dipstick, oil filler cap air intake ducts or vacuum hoses can introduce excess air into the air/fuel mixture, causing rough running or reduced efficiency. Likewise, a plugged hose or passage can cause sludging, stalling and/or oil leaks.



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Fig. Fig. 3: PCV system flow-Accord V-6

TESTING



See Figure 4

The PCV valve is easily checked with the engine running at normal idle speed (warmed up). Gently pinch the hose shut, then release it; the valve should click.

If there is no click, check for plugged hoses or ports. If these are open, the valve is faulty. With the engine OFF , remove the valve from the engine. Shake it, listening for the rattle of the plunger inside the valve. If no rattle is heard, the plunger is jammed (probably with oil sludge) and should be replaced. Never operate the engine without the PCV valve or with the hose blocked.



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Fig. Fig. 4: Gently pinch the hose leading to the PCV valve shut, then release it; the valve should click-Accord V-6 shown

Don't blow directly into the valve in an effort to free the plunger; petroleum vapors and deposits within the valve are harmful.

REMOVAL & INSTALLATION



See Figures 5, 6, 7 and 8

Remove the PCV valve from the valve cover or intake manifold. Remove the hose from the valve. Take note of which end of the valve was in the manifold. This one-way valve must be reinstalled correctly or it will not function properly.



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Fig. Fig. 5: Pliers can be helpful for removing the PCV valve, but be careful not to damage the valve casing

While the valve is removed, the hoses should be checked for splits, kinks and blockages. Some models, are equipped with a breather port and filter on the side of the air cleaner which should also be inspected at this time. Replace the filter if it is dirty or saturated with oil.



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Fig. Fig. 6: Remove the PCV system hoses and inspect them for splits, kinks and blockages



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Fig. Fig. 7: If equipped, remove the screws securing the breather port to the air cleaner ...



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Fig. Fig. 8: ... then remove and inspect the filter. If it is dirty (like this one), it must be replaced

Remember that the correct function of the PCV system is based on a sealed engine. An air leak at the oil filler cap and/or around the oil pan can defeat the design of the system.

 
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