Toyota Repair: 98 Camry tapping noise??, low oil pressure, oil sludge

Question
Hi, I have a 98 Camry 4 cy. It started rattling/tapping between shifts of 1st and 2nd, etc gears. Then it was constant. The oil light did not come on but my boyfried checked it and it didnt show on the stick (I am a typical female...yes, he yelled at me for not checking it more than every 3 months)anyway, he put 3 quarts in it, and we drove it home. Then, after cool, it showed full on the dipstick, the rattling noise is only when the rpms go up and not at an idol. I dont think the car was out of oil, it only holds 4 or 4 and a half qts. Is it possible its just a lifter? My dad says it sounds like its in the top end. Boyfriend thinks Ive done serious damage. What do you think?

Thanks!

Answer
The 5s-fe (4 cyl) engine has had some problems in the past.  over time, the engine oil can jell and block the oil pick up tube, that leads to low oil pressure and lower bearing failure (rod bearings).  i have seen the engine oil jell-up many of times, it'll jell-up even with proper oil changing intervals.  i have also seen those engines spin rod bearings without oil sludge or any sign of problems (i own one that did).  it sounds like that is what happened to yours.  toyota actually had a "special service warranty extention" to cover some problems with that engine......  boyfriend could be right...