The phenomenon of engine backfire explains the reason of engine backfire.

Engine backfire, also known as "backward flow". Simply put, the burned mixture did not leave the combustion chamber in time before and after the exhaust stroke, but ran to the intake pipe through the intake valve to ignite some fresh mixture, accompanied by a "bang" abnormal sound.

Engine tempering phenomenon

In addition to abnormal noise, it also shows that the engine power drops and the car shrugs when accelerating. The common causes of such failures can be divided into two categories: lean mixture and abnormal ignition timing.

1 The mixture is too thin.

The common causes of mixture dilution are: air flow sensor failure, abnormal signal of throttle position sensor, low pressure of fuel system, abnormal coolant temperature sensor, blocked injector, etc.

0 1 ignition time is abnormal.

The common causes of abnormal ignition timing are: abnormal signal of camshaft position sensor, electric leakage of ignition coil, abnormal valve timing, etc.

Routine troubleshooting steps of engine tempering fault:

Maintenance case of engine tempering fault 1

Model: Jetta King car, 5-valve engine

Fault phenomenon:

The engine shakes when idling and backfires when accelerating rapidly.

Fault analysis:

Check the air filter first, and no blockage is found.

Before commissioning, replace the fuel filter and clean the four injectors.

The fault phenomenon still exists. Check whether the fuel pressure, idle speed and acceleration are normal.

Check the air intake system for air leakage.

After taking off the plug of the air flowmeter for trial operation, it is found that the fault phenomenon has been greatly improved.

Check the resistance between terminals of air flow meter, and it is normal.

Observe the resistance, it works well, but it is found that there is dust on the resistance.

Use carburetor cleaner to remove dust, refit and test, and troubleshoot.

Case 2 of engine tempering fault maintenance

Model: Chery QQ

Fault phenomenon: the vehicle can't start, backfire when accelerating after starting, or even stall.

Fault analysis:

Check the system with a diagnostic instrument. There are no fault codes in the system.

First, check the signals of engine timing, camshaft position sensor and crankshaft position sensor, which are all normal.

Then, after removing the intake hose, start the engine again, and the intake pipe emits white smoke, which is usually caused by the blockage of the exhaust pipe.

After the front part is removed, the engine will start smoothly after restarting.

The inspection of the exhaust system found that the lining of the three-way catalytic converter was burnt and bonded.

Troubleshooting after replacing three-way catalytic converter.