ASE A1 Engine RepairCylinder Head and Valve TrainMedium
A technician is diagnosing an engine with a persistent misfire in one cylinder and notices a distinct ticking noise coming from the cylinder head area. Further inspection reveals excessive clearance between the rocker arm and the valve stem tip on the affected cylinder. Which of the following is the most likely cause of this condition?
- AA bent pushrod.
- BAn over-tightened valve spring.
- CA collapsed hydraulic lifter.
- DA worn camshaft lobe.
Show answer & explanationAnswer & explanation
Correct answer: C. A collapsed hydraulic lifter.
A collapsed hydraulic lifter cannot properly take up the lash in the valve train, leading to excessive clearance between the rocker arm and valve stem, which manifests as a ticking noise and can cause a misfire due to improper valve opening.
Why the other options are wrong
- A. A bent pushrod would typically cause erratic valve operation, possible binding, or reduced valve lift, but not necessarily excessive clearance in the way a collapsed lifter does.
- B. An over-tightened valve spring would increase spring pressure, potentially causing premature wear but not directly leading to excessive clearance between the rocker arm and valve stem tip.
- D. A worn camshaft lobe would typically result in reduced valve lift and duration, but the primary symptom of excessive clearance points more directly to the lifter's inability to maintain proper lash.
Collapsed Hydraulic Lifter
A hydraulic lifter that has lost its ability to maintain oil pressure, resulting in excessive valve lash and a characteristic ticking noise.
- Causes excessive valve train clearance.
- Results in a ticking noise from the cylinder head.
- Can lead to insufficient valve opening and engine misfires.
Memory trick: Tick-tock goes the valve, when the lifter's out of groove.