1. Start the engine and let it idle. Go to the exhaust pipe and listen to the sound of the exhaust. You can bring your hand to the cut of the exhaust pipe - so interruptions are felt better. The sound must be even «soft», one tone. Pops from the exhaust pipe at regular intervals indicate that one cylinder is not working due to the failure of the candle, the absence of a spark on it, the failure of the nozzle, a strong air leak into one cylinder or a significant decrease in compression in it. Popping at irregular intervals is due to dirty injector nozzles, heavy wear or dirty spark plugs. If pops occur at irregular intervals, you can try to replace the entire set of candles yourself, regardless of mileage and appearance, but it is better to do this after contacting a car service to diagnose and repair the engine control system.
2. If the pops are regular, stop the engine and open the hood. Check the condition of the ignition wiring harness and the fastening of the wire blocks on the ignition coils. If there is damage to the wires, replace the entire ignition harness.
3. Remove the spark plugs (see «Replacement and maintenance of spark plugs»).
4. Carefully inspect the candles and compare their appearance with the photographs in the subsection «Diagnostics of the engine condition by the appearance of spark plugs».
5. If all spark plugs look good...
6.... check the gap between the spark plug electrodes (only round probe). It should be 1.00–1.13 mm.
7. If the gap differs from the specified, adjust it by bending the side electrode.
8. Install the spark plugs and coils in place and connect the wiring harness pads to them.
9. Disconnect the wiring harness block from the coil of the 1st cylinder. Start the engine. If engine interruptions do not increase, replace the spark plug in the 1st cylinder with a known good one. Put on the high voltage wire and start the engine. If the interruptions have increased, consistently repeat the procedure with all cylinders to identify a faulty spark plug.
If as a result of the measures taken engine interruptions are not eliminated, check the compression in each of the cylinders (see «Cylinder compression check»). Normal compression - more than 1.0 MPa (10 kgf/cm2), the difference in compression values in the cylinders is more than 0.2 MPa (2 kgf/cm2) indicates the need for engine overhaul.