Automotive Service Excellence (ASE) A8 Engine PerformanceGeneral Engine DiagnosisMedium
A technician is diagnosing an engine that occasionally stalls at idle and has a consistent, slight vibration at all RPMs, not tied to engine speed. The vibration is felt more through the chassis than directly from the engine. What should the technician investigate first?
- ATransmission fluid level.
- BA misfiring cylinder.
- CCrankshaft balance.
- DEngine mounts.
Show answer & explanationAnswer & explanation
Correct answer: D. Engine mounts.
A vibration felt more through the chassis and not directly tied to engine speed, combined with stalling, suggests an issue with how the engine's vibrations are being absorbed. Worn or broken engine mounts are a primary suspect for transmitting excess engine vibration to the chassis and can exacerbate stalling issues.
Why the other options are wrong
- A. Low transmission fluid might cause shifting issues or a whine, but typically not a consistent engine vibration felt through the chassis.
- B. A misfiring cylinder would cause a noticeable engine shake/vibration directly from the engine, often accompanied by a rough idle and loss of power, and usually tied to engine speed.
- C. Crankshaft balance issues would cause a vibration directly related to engine RPM and typically felt more directly from the engine itself.
Engine Vibration Diagnosis - Chassis
Identifying the source of engine-related vibrations that are felt primarily through the vehicle's chassis rather than directly from the engine block.
- Chassis vibration often points to engine mounts.
- Engine mounts isolate engine vibration from the vehicle body.
- Can be exacerbated by engine performance issues like stalling.
Memory trick: Vibration's dance, tells the problem's chance.