What causes the popping sound from the exhaust pipe at idle?

[MacKaylee]

Possible causes include fuel line A, fuel line blockage, poor flow, rail pressure, etc. Below is an introduction related to car idle conditions: 1. The function of car idle: Idle is an operating condition of a car, referring to the engine running in neutral gear. The engine speed during idle is called the idle speed. The idle speed can be adjusted by changing the throttle opening size, etc. Idle means the engine "produces power without doing work." When the engine is running, if the accelerator pedal is fully released, the engine is in an idle state. 2. Reasons for unstable idle: Direct causes refer to mechanical parts being dirty, worn, or incorrectly installed, leading to changes in cylinder power, resulting in an imbalance in power among cylinders and causing unstable engine idle. Indirect causes refer to abnormalities in the engine's electronic control system, leading to poor combustion of the air-fuel mixture, making it difficult to balance the power among cylinders and causing unstable engine idle.

[Elena]

I've encountered the issue of exhaust pipe popping at idle quite a few times during my auto repair experience. The main cause is usually unstable combustion in the engine. For instance, when there's a problem with the ignition system - like worn spark plugs or faulty coils - the spark becomes inconsistent, leading to uneven fuel combustion in the cylinders. This creates rhythmic popping sounds during exhaust. Another common factor is an imbalanced air-fuel ratio, possibly due to severe carbon buildup in the throttle body or a clogged air filter affecting air intake, resulting in uneven fuel mixture and strange exhaust noises. It could also be an exhaust system leak itself - loose connections or cracks in the piping causing unstable airflow and popping sounds. I recommend doing some basic checks: after starting the car, observe if the tachometer is steady and check for engine vibration; listen to identify if the sound originates from the exhaust pipe; inspect the dashboard for warning lights. For safety, don't delay too long - get it professionally diagnosed and repaired promptly to avoid damaging core engine components.

[VonRyan]

I've encountered this situation a few times while driving. The idle exhaust pipe popping sound is quite annoying, often a sign of incomplete combustion. Think about it—if too much air gets in or too little fuel is sprayed, the mixture won't burn smoothly, causing the exhaust pipe to make a thumping noise. Common culprits include a faulty oxygen sensor giving the ECU incorrect feedback, leading to poor adjustment, or clogged fuel injectors causing insufficient fuel supply. On the exhaust side, a blocked catalytic converter can also increase pressure fluctuations, making the sound more noticeable. Back when I drove a modified car, I had to replace the exhaust system because of this noise, and it only quieted down after adjustments. For troubleshooting, try lightly pressing the accelerator to observe RPM changes or visually check the exhaust pipe for leaks. Don't underestimate it—address it promptly to prevent it from worsening to the point of breakdown.

[DelEthan]

The intermittent "thumping" sound from the exhaust pipe at idle usually indicates uneven engine operation. Based on my daily driving experience, there are several possible causes. First, weakened spark plug performance leads to incomplete combustion. Second, a stuck idle air control valve or fuel line blockage causes unstable fuel supply. Third, intake manifold leaks introduce excess air, disrupting the air-fuel mixture. These factors create rhythmic thumping noises during exhaust. Simple checks include inspecting for abnormal vibrations under the hood and verifying dashboard warning lights. Prompt repair is advised to prevent more serious issues during high-speed driving.