There are a few different ways to detect a timing belt tensioner failure by driving your vehicle. One thing to remember is that the toothed timing belt is not actually slipping when the tensioner begins to fail. Instead, the tensioner is unable to maintain the correct tension on the timing belt when the throttle is suddenly opened. The crankshaft and camshaft will lose their optimal timing within a minute or two.

Look for the following signs of a timing belt tensioner failure:

Acceleration Problems

Lack of perfect timing can cause acceleration problems. You may notice sluggish acceleration.

Difficulty Starting the Vehicle

When there is a problem with the timing belt tensioner, the valve timing will be slightly off. This can cause difficulty starting. It may take a while for the engine to start properly. Even if you manage to start the engine, the engine may misfire or run rough.

Strange Noises

When the timing belt is not tight enough, it will start to make noises. Or you may hear noises coming from the timing belt tensioner. For example, the pulley may not spin freely. It may start to make a squeaking sound as it spins. When the engine is idling, listen for the following noises coming from the timing cover area: rattles, squeaks or squeals, knocking

Remember that the serpentine belt also has a tensioner pulley and sometimes an idler pulley. Both of these can make the same noises as the timing belt tensioner pulley. They are both relatively easy to check and simple and inexpensive to replace. So if you have questions about the source of the noise, take steps to rule them out first. Also, if they are malfunctioning, they usually won't cause stalling or hard starting.