Audi A4, S4

since 2000 of release

Repair and car operation

Engine check by means of the vacuum gage

Using the vacuum gage, it is possible to receive information on a condition of the engine and to define that laying of a head of the block of cylinders is punched, the power supply system is damaged, rings are damaged, the power supply system is incorrectly adjusted, valves etc. are damaged. Unfortunately, indications of the vacuum gage can be interpreted incorrectly therefore these measurements are necessary for using in a combination to other methods of check of the engine. For the correct definition are important both absolute value of indications of the vacuum gage, and speed of their change.

Basic provisions and fluctuations of an arrow of the vacuum gage at diagnostics of malfunctions of the engine

Connect the vacuum gage to the inlet pipeline. Start and warm up the engine to normal working temperature.

Consider vacuum gage indications. If the engine is in a normal state, indications of the vacuum gage should be 430-560 mm Hg, and the arrow of the vacuum gage should be at a stop.

Low constant indications of the vacuum gage testify that laying between the inlet pipeline and the throttle case is damaged, the vacuum hose is damaged, the moment of ignition or the wrong installation of phases of a gazoraspredeleniye is incorrectly established.

If indications of the vacuum gage are lower than norm on 80-200 mm Hg and hesitate, that, possibly, laying of the inlet pipeline near an entrance opening is damaged or the injector is faulty.

If indications constantly fall on 50-100 mm of mercury. rather stable value, that, probably, valves are damaged. In this case it is necessary to measure a compression in engine cylinders.

If indications fall, but is not regular, that, probably, gets jammed the valve or there is a failure in ignition.

If indications quickly fluctuate with amplitude about 100 mm Hg, at constant turns of idling, and from an exhaust pipe there is a smoke, probably, directing plugs of valves are damaged. If indications quickly fluctuate at increase in turns of idling, that, possibly, laying of the inlet pipeline or laying of a head of the block of cylinders is damaged, springs of valves are weakened, valves scorched or there is a failure in ignition.

Small fluctuations about 25 mm of mercury. are usually connected with failures in ignition system.

If indications strongly fluctuate, that, possibly, laying of a head of the block of cylinders or the cylinder is damaged.

If the arrow slowly moves largely values, that, possibly, the system of operated ventilation of a case is littered, laying of the inlet pipeline or laying between the case of a butterfly valve and the pipeline is damaged.

Check, vacuum gage indications after sharp and complete opening of a butterfly valve and its return to a starting position are how fast restored. If the engine is in a normal state, indications fall almost to zero, then increase approximately on 130 mm Hg above norm and again decrease to former values at constant turns of idling. If indications are restored slowly and pass through a maximum after butterfly valve closing, that, probably, piston rings are damaged. If there is a long delay, that, possibly, the exhaust system is littered.