1. We prepare the car for work (see "Preparing the car for maintenance and repair").
2. We check and, if necessary, adjust the clearances of the timing valve drive (see "Adjustment of backlashes of a drive of valves GRM").
3. We warm up the engine to operating temperature and turn off the ignition.
4. We take out the fuses of the computer and the circuits of the engine management system (see "Relays and fuses of the engine management system").
5. Turn out the spark plugs (see "Spark plugs - check and replacement").
6. We install the compression gauge in the spark plug hole of one of the engine cylinders.
7. The assistant presses the pedal "gas" all the way to the floor (to fully open the throttle) and turns on the starter for 5-10 s.
Note: Measurements must be taken with a fully charged battery, otherwise the readings will be incorrect.
8. Remember, or write down the readings of the compression gauge and reset the device.
9. Similarly, we measure the compression in the three remaining cylinders.
For a serviceable engine, the compression in the cylinders must be at least 1.0 MPa (10 bar), and the difference in compression between the cylinders is no more than 0.1 MPa (1.0 bar).
10. If the compression is less, then pour about 10 cm³ of engine oil into the spark plug holes of the engine cylinders with low compression with a medical syringe or oiler.
11. Repeat the compression test. If the compression has increased, then it is possible "lay down" rings or worn piston group (see "Piston rings and connecting rod bearings - replacement"). Otherwise, the valves do not close tightly or the cylinder head gasket is faulty.
Recommendation: You can try to eliminate the occurrence of valves with special preparations poured into the fuel tank or directly into the engine cylinders (see "instruction" to the drug). The tightness of the valves can be checked with compressed air at a pressure of 0.2-0.3 MPa (2-3 kgf/cm³), supplied through spark plug holes. It is necessary to supply air in such a position of the camshaft when both valves of the cylinder under test are closed. If the exhaust valve is faulty, then air will exit through the exhaust system, and if the intake valve is faulty, through the throttle assembly. If the piston group is faulty, air will escape through the oil filler neck. The release of air bubbles through the coolant in the expansion tank indicates a malfunction of the cylinder head gasket.