Tech line summary article - Have a vehicle in your shop with low mileage (less than 1,500 miles) and a hard-to-pinpoint engine knock? We're currently investigating vehicles for hairline fractures in the crankshaft sprocket, and we suspect it may be the cause for this noise. In some cases you may be able to see these fractures by just removing the crankshaft pulley; however, they can be very small and you may need to remove the cam chain to ensure a thorough inspection.