sometimes when im on red light my cars rpm dips little bit and therefore causing to start wierd chirping noise. when i let off gas pedal cause starts chirping sound. when i put the car in neutral chirping stops. i've had code for camshaft positioning sensors pop the engine light but i raplaced both brand new sensors. but code is still coming up. when car dips rpm at idle causes engine light with camshaft code and here comes chirping noise. when i turn off car and turn on the chirping goes away. but when i do turn off the car, it kinda like squeels off. like that chirping noise slowly going away. when i start the car afterwards it jerks and has loud knock sound. like clunk!!!! ... any ideas?