The purpose of timing gears is to allow the camshaft and crankshaft to turn the timing chain. The crankshaft turns to move pistons up and down inside the cylinders. The camshaft turns to allow intake and exhaust valves on the cylinders to open and close. These components are important for proper engine timing. As the piston moves downward inside the cylinder, the intake valves open to allow fuel and air into the cylinder. As the piston moves upward inside the exhaust the exhaust valves open to expel exhaust valves from the cylinders. If the intake valves are not opening and closing properly, the correct air/fuel mixture will be unable to enter and remain inside the cylinders. If the exhaust valves are not opening and closing properly, exhaust gases will be trapped inside the cylinder.
If the timing gears are going bad or failing and the timing chains are unable to be turned by the camshaft and crankshaft, valve timing and ignition timing will be off. If valve timing and ignition timing are not accurate, noises from the engine compartment may be noticeable. It is also possible that timing gears that are going bad or failing may cause the engine to run rough, backfire and/or not run at all.
1. Rattling noises from the engine compartment
Rattling noises from the engine compartment may be an indication that the timing gears are going bad or failing. There are several things that can cause noises from the engine compartment. Those attributed to timing gear failure could be caused by the timing gear itself, the timing chain rubbing or hitting something it shouldn’t, or the timing chain guides being broken or worn out. This is a symptom that may be present at the start of the problem or as the problem progresses and should not be ignored. Allowing time to progress without addressing noises heard from the engine compartment could cause damage to other engine components.
2. Engine runs rough or backfires
An engine only runs smoothly when all of its components are in working order. The timing gears are an important component of engine and ignition timing. If the timing gears are going bad or failing, the valves may not open correctly to allow air and fuel into the cylinders or close correctly to release exhaust fumes from the cylinders. When this happens, ignition timing will be off because the spark plugs are not being fired in time, or in order. This will cause a rough running engine condition. It may also cause the engine to backfire. This is a symptom that may be present at the start of the problem or as the problem progresses. It should be addressed as soon as possible to prevent total engine failure.
3. Engine does not run
When a timing gear is going bad or failing, the camshaft and crankshaft may be unable to turn the timing chain. As a result the camshaft will be unable to turn in order to open and close the valves. Also, the crankshaft will be unable to turn in order to move the pistons up and down in the cylinders. It is necessary for all of these components to be in good working condition in order for proper engine timing. If the timing gear is faulty and the camshaft and crankshaft are unable to turn, this may result in the engine not running at all. This is a symptom that may be present at the start of the problem or as the problem progresses.
This article originally appeared on YourMechanic.com as Symptoms of Bad or Failing Timing Gears (Gear To Gear) and was authored by Jamahl Walker.