greetings to day my 98 sport developed knocking sound,the engine started idling rough at the same time.when idling the motor never moved now it is visibly shaking not a lot but some it did not do that be for.this leads me to beleive i also have a miss fire.although check engine light is not on i have read about loose flex plate bolts but because of the rough idling i am thinking it could be some thing else.any help or advise would be appreciated this is a high mileage motor over 300,000 miles i am afraid to start it oil pressure is normal and engine did not over heat when this happen engine had only been running for a few minutes i was pulling a small bush out in 4 low if it matters

thank you for the help