Old A6L is a hydraulic directional machine. During directional well killing, the hydraulic oil in the booster system is close to closing because of directional well killing, which leads to pressure rise and high pump shaft rotation resistance. The belt increases the resistance of the engine through the turntable of the booster pump, which makes the engine load too large, which leads to the engine idle speed decrease, unstable jitter and easy flameout. At this time, it is necessary to increase the throttle. Suggest the direction. It will be much better if you settle down after death.