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Having properly functioning exhaust valves is an important part of automobile maintenance as poorly functioning exhaust valves can lead to excessive oil consumption, compression leaks, valvetrain noise and total valve failure. Exhaust valves are more susceptible to burning because they run hotter than the intake valves, averaging between 1,200 and 1,350 degrees Fahrenheit. Most of the time when exhaust valves are burned, they will cause losses in compression. Therefore, a good way to test for a burned exhaust valve is to run a compression test or leak-down test.
Ignition Misfire
A misfire can sometimes be an indication of a burned exhaust valve. Typical signs of a misfire include the engine shaking at idle, steering wheel vibration, or if the engine is difficult to start or stalls at start up. If this is happening, it could mean a loss of compression, which occurs when the cylinder has lost a large part of its air and fuel mixture before being ignited. If not a blown head gasket, misfires due to loss of compression usually mean there is a burned exhaust valve.
Power Loss
Power loss can be another indication of a burned exhaust valve. This is also linked to ignition misfires since a misfiring cylinder can sometimes cause up to 25 percent power loss. If your automobile is losing power, it could mean the exhaust valve is burned.
Puffing or Puttering Sound
A burned exhaust valve will often make noises that sound like a puff or putter. ImperialClub.com refers to it as a "chuff-chuff." These sounds go off each time the cylinder tries to fire. EconoFix.com points to a trick where car owners can hold a dollar bill and let it flap over the exhaust pipe. If it gets sucked in every so often, it is likely a burned exhaust valve.
Failed Emissions Test
If the exhaust pipe is burned, the engine will blow hydrocarbons out of the tailpipe. This will cause many vehicles to fail an emissions test. If your car has recently failed such a test, it could be a symptom of a burned exhaust valve.
