ok my manual says it could be the EST, knock sensor, or bad ECM...well i think it could be the knock sensor because the other day i was outside looking at the motor while it was running and i started to hear knocking/clicking noises under the valve covers then it stopped...could that be the knock sensor?? because after a few minutes the noise stopped and i dont think i broke a pushrod because the car still runs good...what you all think? btw its a 88 305 TBI if that matters

 

I have the exact same problem..the other day i threw a code 43 a nd i have that intermediate sound that comes from under the valve covers. It was doing it today infact, but not often. I hope its nothing bad. I posted about this like a week ago and no one really replied but that was in the tech forum so maybe you'll get better response.

 

i think it might be the knock sensor ill probably replace it soon. i was reading and that noise could be the pushrod broke and its hitting the valve cover but it wouldnt stop it would always do it and it would run like ****