What Causes the Abnormal Noise During Rapid Acceleration in Turbocharged Vehicles?
3 Answers
Turbocharged vehicles may produce abnormal noise during rapid acceleration due to the following reasons: 1. Excessive cam wear causing tappet jumping during operation. 2. Excessive valve clearance due to wear or improper adjustment of the valve stem end and adjusting screw or rocker arm, leading to impact between the rocker arm head and valve top in overhead valves. 3. Excessive carbon buildup in the valve guide. 4. Detachment of the valve spring seat. 5. Damage to the hydraulic tappet or tappet barrel. Additional information: 1. Piston slap noise refers to the abnormal sound produced when the piston side impacts the cylinder wall. Generally, when the direction of axial force on the piston top changes from the compression stroke to the power stroke, piston slap noise occurs. 2. Knocking sound: As the engine temperature rises, the piston clearance decreases accordingly, and the knocking sound will also diminish.
After running an auto repair shop for so many years, the most common cause of abnormal noise during sudden acceleration in turbocharged cars is air intake pipe leaks. When you stomp on the gas pedal, turbo pressure surges sharply. If there's a crack in the pipe or a loose clamp, it'll produce a hissing air leak sound. Some older cars with cracked and aged rubber hoses show more obvious symptoms. Worn turbo bearings can also cause a humming noise, especially during sudden acceleration when RPMs climb. If the blow-off valve fails, you'll hear a sharp whistling sound the moment you release the throttle. For burnt exhaust manifold gaskets, sudden acceleration may produce popping sounds like backfires. I recommend first checking all intake pipe connections—feel around by hand for air leaks. If the issue persists, it's best to use a mechanic's stethoscope to pinpoint the source of the abnormal noise.
Last week, my own car made a whistling sound when accelerating hard, which scared me into getting it checked immediately. The mechanic said the turbo intake pipe connection was loose, and simply tightening the clamp fixed it. These kinds of minor issues are particularly common, especially in cars that are five or six years old, as the rubber hoses harden and are prone to air leaks. Sometimes it's the wastegate sticking, causing a squealing sound during hard acceleration. If it's a bearing failure, the noise resembles metal grinding. After that repair, I specifically learned a little trick: after a cold start, stomp on the accelerator a few times and listen near the engine bay—it's easy to locate the air leak. However, if you hear a metallic rattling sound, definitely don't drive any further and call a tow truck right away.
