INFINITI G37 unable to exceed 20 miles per hour on INFINITI G37

Some INFINITI G37 owners report experiencing a speed limitation where the vehicle is unable to exceed 20 miles per hour due to several potential issues. These problems may include a collapsed catalytic converter, clogged DPF filter, or the ECU engaging limp mode, as well as a faulty transmission. Additionally, some owners have identified a faulty fuel pump or spark plugs as contributing factors to this speed restriction. Transmission issues, such as a mild forward shift or the car feeling like it is in sleep mode, may also play a role. Overheating has been noted as a factor, with some drivers finding that even after cooling down, their vehicle could still only reach around 20 miles per hour. Unusual noises, such as a roaring sound or rough transmission shifts, could indicate further mechanical problems like wheel bearing issues. Specific concerns like grinding in the transmission's 3rd gear or flywheel chattering have also been linked to the speed limitation. It is crucial for owners to diagnose the specific cause to effectively address the underlying problem.