Excessive piston to cylinder wall clearance will cause:

Excessive piston to cylinder wall clearance can lead to a condition known as piston slap. Piston slap occurs when the piston moves too freely within the cylinder, resulting in lateral movement against the cylinder walls. This can produce a knocking or clattering noise as the piston shifts during its travel up and down the cylinder. The extra clearance allows the piston to hit the cylinder wall more forcefully during its motion, which is where the term "slap" comes from.

While oil consumption can be affected by piston clearance, it is primarily caused by other factors, such as worn piston rings or issues with oil control. Pre-ignition is related to combustion abnormalities and is not directly linked to piston clearance. Similarly, connecting rod knock is associated with the clearance between the connecting rod and the crankshaft journal and not directly with piston-to-cylinder wall clearance. This is why piston slap is the primary concern when there is excessive clearance in this area.