- Timing chain tensioners are responsible for controlling the tension of the timing chain, keeping it tight to ensure that it runs smoothly.
- Bad timing chain tensioner symptoms include a lit check engine light, engine performance issues, and rattling noises from the engine.
- Timing chain tensioner problems are often brought about by poor maintenance and forgetting to get oil changes.
Some vehicles have a timing chain (instead of a timing belt) buried inside of the engine. Although the timing chain and related components, such as the timing chain tensioner, are designed to last the life of the vehicle, that doesn’t always happen.
A failed timing chain tensioner can lead to significant engine damage—and that’s definitely something you’ll want to avoid. If your vehicle has a bad timing chain tensioner, you’ll notice some obvious symptoms that you’ll want to address right away.
What Does a Timing Chain Tensioner Do?
Before you can comprehend the role of the timing chain tensioner, you need to have an understanding of the timing chain. Inside the engine, there are is a crankshaft and one or more camshafts. The crankshaft is attached to the connecting rod and piston assemblies, whereas the intake and exhaust valves are operated by the camshaft(s).
The crankshaft and camshaft(s) must be kept in sync (“in time”) so that the pistons are at the correct point of travel when the valves open and close. Depending on the engine design, either a timing belt or timing chain is used to connect the crankshaft to the camshaft(s), thereby keeping the engine in time.
One or more tensioners and a collection of guides are used to secure and keep tension on the timing chain. Depending on the engine’s design, the tensioner will use either spring tension or oil pressure to keep the timing chain tight.
The timing chain must be kept secure so that engine timing remains within specification. Otherwise, the engine will experience performance problems, such as rough running and misfiring. There could even be catastrophic internal damage from valve-to-piston contact.
Bad Timing Chain Tensioner Symptoms
Do you think you might be dealing with a bad timing chain tensioner? If you notice one or more of the following symptoms, you might be right.
Note: Other problems can mimic a failed timing chain tensioner. You (or your mechanic) should perform a thorough diagnosis before conducting any repairs.
Illuminated Check Engine Light
The engine computer, which is often referred to as the powertrain control module (PCM), monitors engine timing via the crankshaft and camshaft sensors. If the PCM determines the engine timing is off due to a failed tensioner or any other problem, it will turn on the check engine light and store a diagnostic trouble code (DTC) in its memory.
Engine Performance Problems
An engine needs three ingredients to run well: proper spark, a precise air-fuel mixture, and adequate compression. Compression—the pressure the piston imposes on the air-fuel mixture while moving upward in a sealed cylinder—is necessary for the air-fuel mixture to be ignited properly.
When the engine is out of time due to a failed timing chain tensioner, the valves don’t open and close when they should, leading to a loss of compression and an engine that runs rough and misfires.
Engine Cranks But Doesn’t Start
In some cases, the engine might not even start if the tensioner fails and the timing chain breaks or becomes extremely loose. In such a scenario, there’s a good chance the valves will remain open when they shouldn’t be, resulting in valve-to-piston contact and catastrophic engine failure.
Rattling Noise From the Engine
A failed tensioner will cause the timing chain to be loose, which can result in a rattling noise coming from the engine. If the engine has hydraulic tensioners, you might notice that the noise is most prominent upon start-up when oil is just beginning to circulate throughout the engine.
Usually, timing chain tensioners simply wear out over time. A tensioner may also become over-extended if the timing chain is stretched. Lack of maintenance (oil changes) can lead to accelerated timing component wear, as well.
On most modern vehicles with second-generation onboard diagnostics (OBDII), an engine that’s out of time will usually set one or more timing-related DTCs that can be retrieved with a scan tool or code reader. But to determine whether the timing chain tensioner is to blame, you’ll need to access the tensioner and perform a visual inspection.
In many cases, you must remove the timing cover to inspect the timing chain tensioner directly. Though, in some instances, you might be able to see the tensioner through an inspection cover or by removing the valve cover and looking down at the timing components.
If the timing chain tensioner shows visible damage or is over-extended, it has failed (or the timing chain is stretched). Some timing chain tensioners also have seals that blow out, but you generally need to remove the tensioner from the engine to check the seal.
You absolutely should not continue to drive with a bad timing chain tensioner. Doing so can cause catastrophic engine damage and potentially leave you stranded.
Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.