Repair Review Car

1. Buy a timing chain that is made specifically for the BMW 525i 2.5L engine. Most auto parts store or online vendors carry the timing chain needed. Lift the hood of your vehicle and disconnect the negative battery cable. Remove the vibration damper and hub assembly to reach the upper and lower timing case covers. Remove case covers. Refer to the vehicle service or owners manual to identify vehicle parts.
2. Use a ratchet and pinch the upper timing chain tensioner to hold it in place. Use a wrench to remove the upper timing chain sprockets. Remove the camshafts that run along the side of the timing chain. Loosen bolts holding the upper timing chain guide in place. Remove the timing chain and upper timing chain guide. Remove the ratchet holding the upper timing chain tensioner. Remove the crankshaft sprocket and tensioning rail if necessary. Remove the Woodruff key.
3. Install the new timing chain. Replace the Woodruff key and reattach the crankshaft sprocket and tensioning rail. Reattach camshaft sprockets and tighten bolts using a wrench to 16 foot pounds (22Nm). Reattach and tighten lower timing cover bolts to 6.5 to 8.0 foot pounds (9 to 11Nm). Reattach the vibration damper hub bolt and tighten to 17 foot pounds (23 Nm).
4. Replace the upper and lower timing case covers. Start the engine to make sure the timing chain is installed properly.

1. Place the BMW’s transmission into Park (automatic) or neutral (manual transmission) and apply the parking brake. Leave the engine running.
2. Connect a scan tool to the BMW’s diagnostic data port, which is under the dashboard just above the pedals on the driver’s side.
3. Power on the scan tool and choose “Bi-Directional Tests” from the main menu. Select “IAC Valve Actuation” from the tests menu.
4. Use the scan tool’s buttons to open and close the IAC valve. The idle speed should rise and lower without pressing the accelerator. If the IAC valve does not respond to the scan tool by raising and lowering the engine idle speed, then it is faulty.