Home › Forums › Stay Dirty Lounge › Service and Repair Questions Answered Here › 96 Thunderbird knocking,lack acceleration,smoking › 96 Thunderbird knocking,lack acceleration,smoking January 22, 2020 at 2:09 am #895860 Richard KirshyParticipant Piston slap, rod knock, dropping a valve or valve seat or spun bearing. In any case it doesn’t bode well for that engine.