Honda Accord/Prelude 1984-1995 Repair Guide

Positive Crankcase Ventilation (PCV) Valve


See Figure 1

The engine is equipped with a Positive Crankcase Ventilation (PCV) system in which blow-by gas is returned to the combustion chamber through the intake manifold and/or the air cleaner. Blow-by gas is the portion of the normal combustion gasses that get by the piston rings and pressurize the lower part of the engine. If not vented, these gasses will eventually force their way through gaskets at the top or bottom of the engine, causing improper running and/or fluid leaks.

The PCV system captures these gasses and routes them back into the engine where they can be reburned. The PCV valve controls the flow into the engine. If the valve sticks closed, excess pressure can build in the engine. If it sticks open, too much gas may be admitted to the engine, causing a rich mixture, black exhaust smoke and generally poor driveability.

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Fig. Fig. 1: PCV valve and breather hose location on 1989 Preludes. All models are similar

The function of the PCV valve should be checked every 60,000 miles (96,000 km) or whenever an emission-related problem is being diagnosed. As long as the valve is functioning properly, it does not need replacement.


See Figures 2 and 3

Inspect the hoses for cracks, leaks or clogging. With the engine running at warm idle, use fingers or pliers to gently pinch the PCV hose running to the valve. You shoud hear the valve click when the hose is pinched.

On some models, it will be necessary to remove the air cleaner support brace to access the PCV valve.

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Fig. Fig. 2: If necessary, remove the nuts securing the brace, then remove it from the air cleaner

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