1993 Gen 2 Paj. 4D56 engine. Lately, may narinig akong tapping sound sa may engine bay.I said tapping sound kasi mukhang mas malakas naman ata pag sinabi kong knocking sound.Kung nakasakay ka sa loob you can hardly, if not, hear it.Pag binuksan mo yung hood may maririnig kang tak tapos mga 1 second or more tak ulit.Minsan either wala o mas mahina yung tunog.Pag inapakan ang gas pedal, while the A/T is at N, same frequency ng tunog nya.Di nagbabago.No change in fuel consumption.Wala din naman nagbago sa acceleretion sa pakiramdam ko.What could be the problem here?Thanks for the help!