What is the toyota rav4 noise while accelerating?

The Toyota RAV4 froM2001-2020 has employed a timing chain to control engine firing. If You're hearing a rattling on start-up it could be related to a loose tensioner or stretched chain. This is a serious issue because it will affect engine timing, may break and cause engine failure. More common reasons a "rattling" is heard while accelerating include a loose heat shield or some other part of Your car's exhaust assembly. The wrong octane of fuel can cause a "pinging" sound and bad spark plugs mIS Firing could be mistaken for rattling as well. However, more likely, loose transmission or motor mounts may be vibrating as You accelerate. The cost to repair a loose heat shield ranges from $250-$300 in parts and labor.