Exhaust valves and air intake valves at the top of the cylinder can also get overheated, and leak gas or the valve seals can become too worn to seal the gas in properly. Either way, the result is often low compression. Several valve problems can lead to low compression.

What causes lack of compression in an engine?

Compression loss is a result of a leak in one or more of the cylinders caused by normal engine wear and tear. If you experience compression loss in one cylinder of the engine, it can cause misfiring and poor vehicle performance. A decrease in power output is a sign of worn-out internal parts.

Can bad valve adjustment cause low compression?

Just because compression readings may be low does not automatically mean your valves need adjustment. All a low compression reading is telling you is that something isn't sealing correctly. It could be due to a bad valve to seat interface.