When a vehicle registers 70 psi in Cylinder 3, what is the most probable reason for this low reading?

A low compression reading of 70 psi in a cylinder, such as Cylinder 3, often indicates that there is an issue preventing proper sealing or compression within that cylinder. If we examine the reasons a leaking intake valve would cause this specific problem, it's important to understand the role of intake valves in the combustion process.

When the intake valve does not close properly, air and fuel mixture can escape back into the intake manifold rather than being compressed in the cylinder. This loss of pressure directly translates to a lower compression reading. A leaking valve can be caused by wear, debris, or improper seating, all leading to reduced performance of the engine and the possibility of misfiring, rough idling, or lack of power.

While other options such as piston ring damage or timing belt failure can also impact compression, these would typically affect multiple cylinders or produce different symptoms. Piston ring damage primarily leads to oil consumption and blue smoke from the exhaust, while a faulty timing belt could result in the engine not running or being out of time entirely. A clogged fuel filter would cause performance issues related to fuel delivery, but it would not directly affect compression readings in a cylinder.

Understanding these dynamics clarifies why a leaking intake valve is the most probable cause of a low