What Causes Abnormal Engine Noise During Acceleration?
4 Answers
Abnormal engine noise during acceleration is caused by irregular engine speed conditions during operation. Below are the specific reasons for abnormal engine noise: 1. Noise occurs only at idle or low-speed operation: Excessive clearance between the piston and cylinder wall; Over-tight piston pin assembly or connecting rod bearing assembly; Excessive clearance between the tappet and its guide hole; Wear on the camshaft profile; Sometimes, a loose starter clutch causes pulley noise (noticeable during speed changes). 2. Noise becomes chaotic at a certain speed, with brief sounds emitted during rapid deceleration: Cracked camshaft timing gear or loose fixing nut; Broken crankshaft; Loose piston pin bushing; Excessive axial clearance of the camshaft or loose bushing. 3. Noise appears during rapid engine acceleration and persists at high-speed operation: Loose connecting rod bearings, melted or incorrectly sized bearing shells causing rotation; Loose crankshaft bearings or melted bearing shells; Broken piston pin; Broken crankshaft.
When you stomp on the accelerator while driving and hear a metallic ticking sound from the engine compartment, especially more noticeable when going uphill, this is usually a knocking phenomenon. The difference between domestic 92/95 gasoline grades is significant, with lower-grade gasoline having poor anti-knock properties. Combined with carbon deposits in the cylinders forming hot spots, it can easily cause pre-ignition. Additionally, leaks in the intake and exhaust systems can produce a hissing sound, such as loose turbocharger pipe joints. Last week, I helped a friend troubleshoot a similar issue and eventually found that his long-term use of 92-octane fuel from small gas stations caused a leaking sound near the catalytic converter. Switching to 95-octane fuel from a reputable gas station made a big difference. If you encounter this situation, don't push it; go to a chain auto repair shop for a free inspection first.
I know exactly what you mean about engine acceleration noises, especially with older cars. Last time I drove my old car with 200,000 kilometers on it, I heard a squealing sound when accelerating - turned out to be a worn-out alternator belt slipping. The belt was cracked like a dried-up riverbed, and during rainy seasons it would often make sharp rubber friction noises. Pay special attention to the belt tensioner and idler pulley bearings - these small components only cost around a hundred bucks but can be life-threatening if they fail. During my last maintenance, the technician used a stethoscope to detect abnormal noise from the water pump bearing - catching it early saved me thousands in repair costs. I recommend having mechanics use a stethoscope to check both front and rear engine components during every maintenance session - preventive maintenance is always better than breaking down on the road.
If you hear a chain rattling noise during cold start acceleration, be cautious about the timing system. My brother's German car had a similar issue at 100,000 kilometers - the metal grinding sound intensified with increasing RPMs, and it was eventually diagnosed as a loose chain caused by clogged oil passages in the hydraulic tensioner. Never ignore such abnormal noises, as chain skipping could bend valve stems. Last year, a neighbor used cheap, low-quality oil which caused sludge to block the tensioner's oil passages, leading to similar failure and costing over 8,000 yuan in repairs. Always use genuine full synthetic oil now and regularly check the oil dipstick level.
