One of the most effective methods for diagnosing a motor is determining the appearance of spark plugs. The color of the cone ceramic insulator serves as an accurate indicator of the performance of each cylinder. If an abnormality in the fuel mixture occurs, the spark plugs react quickly by changing the color of the center electrode insulator. So, due to deterioration in engine performance, the color of the spark plug can change within a few seconds.
To carry out this check, make a control trip by car for 15 minutes. In this case, the manual air damper control mechanism is not used. After the trip, the candles are unscrewed and laid out according to the cylinders where they worked. Black carbon deposits on the spark plugs indicate abnormalities in the air-fuel mixture due to clogged muffler, late ignition, rich fuel mixture. With these engine malfunctions, all candles have the same black appearance. When one of four candles turns black, a malfunction in the corresponding cylinder can be detected, as well as a malfunction of the plug itself, its high-voltage wire or tip. For a more accurate identification of the cause, swap the places of the black and any of the clean candles and again make a 15-minute control trip. If, as a result, the black candle has cleared, and the clean one has turned black, this means that there is a malfunction in the cylinder in which the candles turn black. If a black candle remains black, and a clean one is clean, this indicates a malfunction of the black candle. Instead of rearranging the candles in places, they completely change the set of candles to a known good one. If the results of the test trip on a new set of spark plugs turn out to be similar, the fault should be looked for in the cylinder. If the second set remains completely clean after the trip, the black plug from the first set is faulty. In addition, the plug malfunction is felt by the jerks of the car when driving. The features of the blackening of the insulator on the candles also mean a lot. In case of unilateral blackening, when one side of the insulator is black and the other is light, the cause of the phenomenon may be a leaky fit of one of the valves, a burned-out valve, a sticking of the valve stem in the guide sleeve, incorrect installation of the timing belt, a violation of the throughput of the exhaust system. and the top of the insulator and the metal electrodes remained clean, this means that the spark plug does not match the glow number for this engine. It should be replaced with a hotter one for this number. Conversely, a dazzling white spark plug means that it is too hot on the glow number for this motor.
