Fuel supply system malfunction

进气管出现回火是由燃油供应不足，混合气过稀引起。混合气过稀使混合气燃烧速度减慢，燃烧一直延续排气行程终了进气门开启的时候，新鲜混合气遇到气缸内未排净的燃烧气体而被点燃，并逆流经进气歧管从进气口喷出而回火。

The occurrence of backfire in the intake pipe is caused by insufficient fuel supply and a lean mixture. The mixture is too lean, which slows down the combustion speed of the mixture. The combustion continues until the exhaust stroke ends. When the intake valve opens, the fresh mixture encounters the combustion gas that has not been completely discharged from the cylinder and is ignited. It then sprays out from the intake port through the intake manifold and backfires.

点火系故障

Ignition system malfunction

进气管出现回火是因为点火过晚或火花质量差。一方面使开始燃烧的时刻推迟；

The occurrence of backfire in the intake pipe is due to late ignition or poor spark quality. On the one hand, it delays the start of combustion;

另一方面也会使燃烧速度减慢，从而导致燃烧一直延续到进气门开启，引起进气管回火。同时伴随的现象还应有：发动机加速时转速提高缓慢，急加速时回火现象明显，有时缓加速时也有回火现象，同时排气管排气声发闷，发动机温度易升高。

On the other hand, it can also slow down the combustion speed, leading to combustion continuing until the intake valve opens, causing the intake pipe to backfire. At the same time, accompanying phenomena should also include: slow increase in engine speed during acceleration, obvious backfire phenomenon during rapid acceleration, and sometimes backfire phenomenon during slow acceleration. At the same time, the exhaust sound from the exhaust pipe is muffled, and the engine temperature is prone to rise.

如果在进气管回火的同时，机体抖动严重，排气管放炮，发动机功率严重下降，则多是由点火错乱而引起的。由于点火错乱，当某缸处于进气行程进气门开启，恰好该缸火花塞点火，则会形成进气管回火。

If the engine shakes severely, the exhaust pipe bursts, and the engine power drops significantly while the intake pipe backfires, it is mostly caused by ignition misalignment. Due to ignition misalignment, when a certain cylinder is on the intake stroke and the intake valve opens, and the spark plug of that cylinder ignites, it will form a backfire in the intake pipe.

如果检查确认各缸分高压线没有插错，则多为分电器盖击穿。需要引起注意的是分电器盖存在轻微击穿时，一般情况下发动机在无负荷空转时工作正常，但在热车重负载爬坡时有回火现象，且回火时动力明显下降。

If it is confirmed that the high-voltage lines of each cylinder are not inserted incorrectly, it is mostly due to the breakdown of the distributor cover. It should be noted that when there is a slight breakdown in the distributor cover, the engine generally works normally when idling without load. However, there is a phenomenon of backfire when climbing a hot vehicle with heavy loads, and the power significantly decreases during the backfire.

如果发动机空转时工作正常，急加速或急减速时有时回火；高速行驶时有不规则的回火现象；在不平道路上行驶时回火频繁，对于传统有触点点火系来说多因分电器搭铁不良，对电子点火系来说可能是点火器等搭铁不良或点火系某传感器松动等。搭铁不良的分电器或点火器当发动机振动较大使分电器搭铁时，相当于低压回路断开，产生高压电。若分火头正好指向某个处于进气行程的气缸，则会引起进气管回火。

If the engine operates normally while idling, and sometimes backfires during sudden acceleration or deceleration; Irregular tempering phenomenon during high-speed driving; When driving on uneven roads, frequent backfire may occur. For traditional ignition systems with contact points, it is often due to poor grounding of the power distributor. For electronic ignition systems, it may be due to poor grounding of the igniter or a loose sensor in the ignition system. A poorly grounded distributor or igniter. When the engine vibrates heavily and the distributor is grounded, it is equivalent to a disconnection of the low-voltage circuit, generating high-voltage electricity. If the ignition head points directly at a cylinder in the intake stroke, it will cause the intake pipe to backfire.

对于无分电器双缸同时点火的点火系来说，急加速时出现回火现象还有一个常见的故障原因，那就是火花塞不良。在

For ignition systems with dual cylinder ignition without a distributor, a common cause of backfire during rapid acceleration is poor spark plug. stay

检查高压线无漏电、断路后，试换火花塞不失为上策。

After checking that there is no leakage or open circuit in the high-voltage line, it is still best to replace the spark plug.

机械故障。

Mechanical failure.

如果发动机低速运转时进气管回火。排气管有“突突”声，转速提高后症状减轻，则应检查某气缸压缩压力比正常值是否低0．2MPa以上。若将此缸断火，回火现象消失，则说明该缸进气门密封不严。电于进气密封不严，该缸作功时，燃烧的高温气体便会通过进气门进入进气歧管，引起进气管回火。因为发动机转速提高后，气门的相对漏气率降低，因此回火现象在低速时明显，高速时减轻。

If the intake pipe backfires when the engine is running at low speed. If there is a "popping" sound in the exhaust pipe and the symptoms alleviate after the speed is increased, it is necessary to check whether the compression pressure of a certain cylinder is lower than the normal value by more than 0.2MPa. If the cylinder is turned off and the tempering phenomenon disappears, it indicates that the intake valve seal of the cylinder is not tight. When the intake seal of the electric cylinder is not tight, the high-temperature combustion gas will enter the intake manifold through the intake valve when the cylinder is working, causing the intake pipe to backfire. Because the relative leakage rate of the valves decreases as the engine speed increases, the phenomenon of backfire is more pronounced at low speeds and less pronounced at high speeds.

如果发动机工作时，连续有节奏地出现回火，同时动力下降某缸断火后，回火现象消失，则多是因为该缸排气门调整螺栓松脱或推杆折断，使该排气门无法开启或开度过小。由于排气门不能完全开启，使得该缸废气不能及时完全排出，在进气门开启时，尚未排出的高温废气便进入进气歧管，引起进气管回火。可用断缸法找出故障缸，然后打开气门室盖，检查该缸排气门螺栓及推杆是否异常。

If the engine experiences a continuous and rhythmic flashback while working, and the flashback disappears after a certain cylinder is shut off due to a decrease in power, it is mostly because the exhaust valve adjustment bolt of the cylinder is loose or the push rod is broken, making the exhaust valve unable to open or opening too small. Due to the incomplete opening of the exhaust valve, the exhaust gas in the cylinder cannot be completely discharged in a timely manner. When the intake valve is opened, the high-temperature exhaust gas that has not yet been discharged enters the intake manifold, causing the intake pipe to backfire. The cylinder failure method can be used to identify the faulty cylinder, then open the valve cover and check if the exhaust valve bolts and push rods of the cylinder are abnormal.

如果发动机工作时，进气管连续回火，低速时更明显，相邻的两缸中某缸断火。回火现象消失。则可能是因为相邻两缸之间的气缸垫烧穿。因为相邻两缸之间的气缸垫烧穿，使某缸做功时，燃烧着的混合气进入相邻气缸，若此时这个缸的进气门处于开启状态，则会形成进气管回火。可用断缸法找出工作不良的两个气缸，检查两缸的配气机构，如电控失调或元件及线路有故障，也会导致混合气过稀，进气管回火放炮。

If the intake pipe continuously backfires while the engine is operating, it is more pronounced at low speeds, and one of the adjacent cylinders misfires. The phenomenon of tempering disappears. It may be because the cylinder gasket between adjacent cylinders is burned through. Because the cylinder gasket between adjacent cylinders burns through, when a certain cylinder does work, the burning mixture enters the adjacent cylinder. If the intake valve of this cylinder is in an open state at this time, it will form a backfire in the intake pipe. The cylinder cut-off method can be used to identify the two cylinders that are not working properly, and to check the valve distribution mechanism of both cylinders. If the electronic control is out of control or there are faults in the components and circuits, it can also cause the mixture to be too thin, and the intake pipe to backfire and explode.