When I go over a certain speed my accelerator pedal starts to vibrate a little.
My car has an automatic transmission.
Hi there - if by "go over a certain speed" - you mean vehicle speed, the vibration could be a worn CV joint or worn motor mounts, allowing more engine vibration than should be expected. If you mean engine speed, there may be a worn serpentine belt tensioner, or loose belt, which is creating more vibration through the engine itself. It is also possible that the torque converter has an issue causing engine vibration. I recommend a vibration inspection performed by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, give you an accurate assessment of damage and cost estimate for repairs.
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