Nissan Repair: 93 Nissan Altima GXE, nissan altima, step dad

Question
I have a knocking sound coming from either right beside or under the oil cap. my step dad thinks its the timing belt, but my boyfriend thinks different. I'm scared to really drive it till i know what is wrong. i have had problems in past of it shutting off, but according to my step dad it no longer does that. What do you think it could be?

Answer
Hi Heather -

Is it more of a tapping sound than knocking? Does it increase in tempo as the engine rpm's increase? Can you still hear it while driving? Is the car running OK otherwise?

The more info you can give me about this noise, the better, as obviously I am not able to be there to hear it.

Let me know -
aloha
calvin