How to detect malfunction of the intake valve

The component is checked in two stages. First, all systems are checked on a specialized bench with a computer.

Then, the system is disassembled, and the valve is dismantled. Inspect the component to check for absence of carbon deposit and mechanical damage. Special attention should be paid to adjusting the valve, and its position in the seat. Before proceeding to the latter, the engine is to be cooled down. Then set the piston into the top dead center of the compression stroke. Then loosen the second nut screwed after the main one, and adjust the clearance using a gauge. The optimum clearance should allow the gauge inside with perceptible effort.

Note that the valves cannot be adjusted separately from other components. So, after

replacing the valve, remember to reseat the new component in place.

You may notice that the intake valve may need diagnostics by the following symptoms:

• the engine knocks, and other extraneous sounds are heard in all operating modes;
• the engine misfires;
• consumption of fuel and motor oil increased;
• the engine works incorrectly at low rpm, and spontaneously stalls at idle.

The reasons of the intake valve malfunctions

Malfunction or complete failure of the component may be caused by using poor quality fuel or motor oil. Using low-octane gasoline leads to low anti-knock value of the fuel, which results in high loads on the piston group. Consequently, the working temperature of the engine increases. Carbon deposit is also accumulated on the valve head, which, after reaching certain thickness, detaches and gets between the seat and the valve face. This results in overheated valve head and impaired contact with the seat.

Often the reason of the component malfunction is an increased or decreased clearance between the seat and the valve. The greater the distance is, the faster the component wears out, and the engine fails. If the clearance is less than normal, the intake valve stops performing its functions. Thus, fuel does not get into the cylinders in time. Operating a vehicle with closed valves results in engine overheating and premature failure of the cylinders.

The reason of the intake valve burn-off may be a too late or, vice versa, too early ignition. Therefore, if the component fails, it is necessary to make sure that the ignition advance angle is correct.

Replacing an intake valve

Repair cannot remove even insignificant defects of the valve, therefore it is expedient to replace it.

To dismantle the component, first remove the timing belt and the camshaft cover. It is recommended to mark the sequence of rockers and compensators with a marker.

To tighten the bolts of the camshaft cover, use a torque wrench. The tightening torque should the only 10 Nm.

To make the valves wear out evenly, replace all components at once.