Some 2005-2010 Ford Mustangs equipped with a 4.0L engine may exhibit a buzz noise from the upper engine at about 1,900 rpm under light load acceleration.
1. Prior to normal diagnostics, check the fasteners that attach the ignition coil bracket to the intake manifold for proper torque. If the bolts are found to be torqued under 89 in.-lbs., proceed to Step 2. If the bolts are torqued correctly, this procedure doe not apply. Follow normal diagnostics.
2. The ignition coil bracket to intake manifold bolts are intended to be tightened by a torque-plus-angle method. Torque both bolts to 89 in.-lbs., and then tighten an additional 45 degrees.