Pontiac Repair: 97grandprix se, oil pressure gauge, low oil pressure

Question
When I start my car after letting it sit for a period of time, it makes a tapping sound. I'll let it run for a few minutes and take off. The sound goes away after a couple of minutes. A friend of mine told me that my oil pump is going bad. Would that be a good assumption? How difficult would it be to change, and much would it cost me?

Answer
Hi John:

Does the tapping sound seem to be going at 1/2 the engine speed or at the same speed as the engine.  It may be a lifter going bad or it could be low oil pressure. either way it's a mechanical issue. I would first put a mechnaical oil pressure gauge on the car and let it get good and hot and see what your oil pressure is at idle spped. I doubt it's an oil pump issue it' more like parts are just old and worn out and you have excessive clearance between engein parts and that is causing low oil pressure or like I said if it's 1/2 enegin speed maybe a lifter going bad or sticking. If it's got good pressure and the noise is 1/2 the speed try a product called marvel myster oil in the crank case follow the directions on the can and see if that works. Good luck :)