Is an ignition advance angle of -10 normal?
3 Answers
An ignition advance angle of -10 is not normal. The reason for a negative ignition advance angle is a malfunction in the knock sensor. Below are the methods for adjusting the ignition timing: 1. Adjust the gap: Check the contact gap of the damaged electrical components and adjust if necessary. The normal contact gap is 0.35 to 0.45mm. 2. Adjust the cylinder piston top dead center: Manually rotate the engine to position the first cylinder piston at the top dead center of the compression stroke. The method involves removing the spark plug of the first cylinder, blocking the spark plug hole on the cylinder head with a finger, and turning the crankshaft. When atmospheric pressure is felt, slowly rotate the crankshaft to align the timing mark or pointer with the specified symbol.
As a long-time auto mechanic, I've seen many ignition timing issues, and negative 10 degrees is clearly abnormal. Generally, the ignition angle should be above 0 degrees, igniting the air-fuel mixture before the end of the engine's compression stroke to generate maximum explosive force. A negative angle means the ignition timing is too late, resulting in incomplete combustion of the mixture, directly leading to reduced power and significantly increased fuel consumption. Common causes include inaccurate crankshaft position sensor signals, timing belt misalignment, or abnormal ECU programming. This issue can range from minor to serious, so I recommend connecting a diagnostic tool to read fault codes as soon as possible, and checking the sensor wiring and timing marks for alignment. I once encountered an old Accord with a similar issue—the owner drove it for two months without fixing it, and in the end, even the spark plugs were burned out.
Last month, my car experienced abnormal ignition timing, and I noticed it was particularly sluggish when accelerating—even with the throttle fully depressed, the speed wouldn't increase. I specifically borrowed a friend's OBD scanner to check the readings and found that the advance angle at idle was fluctuating around negative 10 degrees. Later, it turned out that the wiring for the knock sensor had been gnawed by mice, causing the engine control unit to misjudge engine knocking and deliberately delay ignition. After replacing the damaged wiring harness myself, everything returned to normal. If you encounter a similar situation, I recommend first listening for any metallic rattling sounds from the engine and checking if the exhaust pipe emits black smoke. These signs indicate combustion issues, and prolonged neglect could even lead to the failure of the catalytic converter.
