The BMW Timing Chain consists of a long chain that runs from a gear on your engine’s crankshaft to gears on your engine’s camshafts. True to its name, the timing chain determines the valve timing of your engine. If it’s off by a tooth or two on the gear, your engine either won’t run or won’t run well. Likewise, if the timing chain stretches over the years, you can get symptoms similar to that of a timing chain that has jumped a tooth.

You may have heard of timing belts, and they do the same thing as a BMW timing chain—they just use a belt to drive the cam gears. The BMW timing chain is a slightly noisier design, but it has the advantage of an extremely long service life and very precise timing. All metal parts do wear eventually, however, so if you find inexplicable rough-running issues on a high-mileage engine, the BMW timing chain is one place to look.