Rough idling engine in conventional ignition system
The causes of idling engine
(1) Distributor cap is dirty, damaged and leakage of electricity.
(2) Damage of  high-tension lead  leakage, loose, fracture.
(3) The high-voltage conductor is inserted incorrectly.
(4) Open circuit and short circuit in the primary winding and secondary winding.
Spark plug carbon deposition
(6) Spark plug electrode burning loss or the gap is too large.
(7) The initial ignition advance angle is too large.

The engine can start, but the engine runs unsteadily or even stops at idle speed. When accelerating, the exhaust pipe sounds like rur ..rur.. rur…Engine power is obviously insufficient.
This kind of fault phenomenon is generally due to individual cylinder not working or working bad, ignition timing is abnormal and other causes.

(1)Check the working condition of each cylinder of the engine
When the engine is running at idle speed, adopt misfire detection method (make the high-tension lead of the tested cylinder short circuit or open circuit, result in the cylinder misfire). Observe the changes in engine operation. If the engine speed does not change or the change is small, indicate the cylinder does not work or work bad. If the engine speed drops obviously, it indicates that the cylinder works normally. Then, check other cylinders in turn. If the engine speed drops when each cylinder misfire, the next fault diagnosis shall be made.

(2)Check the strength of each cylinder spark
Pull-out high-tension lead and conduct the jump spark test to see if the spark is strong. If the spark is strong, check and adjust the ignition timing and spark plug, if the spark plug is in good condition, the ignition timing is correct or the engine idle speed is still unstable after the ignition timing is adjusted, then the oil circuit shall be checked or adjusted. If the spark is weak, check the breaker contact, ignition coil, distributor cap, rotor, etc.
(3)Check whether the cylinder spark jump
Pull out the high-tension lead of the cylinder and conduct the spark jump spark jump test to see whether spark jump. If not, check distributor cap, high tension lead; If there is spark jump, check the spark plugs and repair or replace them if necessary.
James Smith        July 15, 2020

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