Tapping after oil flush

[dallenx]

Posting here as well as 2.3 forum, hoping you guys & girls can help. thanks

I picked up an '89 LX this weekend and since there were no service records, I took it home to start a tuneup.
I put about 150mi on the car before the tuneup and had no problems but low oil pressure (got lower the more I pressed the throttle and would come back up when I let off).

Oil maintenance:
1) I flushed the engine then drained it.
2) Put on a Fram High Mileage filter.
2) Put in Slick50 High Mileage additive.
3) Put in Castrol High Mileage 10w-30.

Ignition maintenance:
1) New dist cap
2) New rotor.
3) New Napa Belden Max wires.
4) New Autolite plugs

Start the engine up with no problems.
After about 60sec a tapping starts to develop.
Sounds like it's coming from around #3cyl.
Tapping goes away / or least quites down with increased RPMs.
Shut the engine off and start right back up.
Tap comes back in about 5sec now.
Left the car over night......
Start up next day and no noise for first 30sec.

Oil pressure is now in the middle of the 'normal' range at idle (hangs around the letter 'm').
Drive the car and the oil pressure drops a little but now the pressure increases slightly back to around the letter 'M' when accelerating instead of dropping to 'L' like before.

What gives?

 

[TheBocSez]

Could be several things. Of course low oil pressure can be associated with excessive bearing clearances. With a high milage motor, could be that.

Could also be that the the oil pump pick up screen is clogged. This could have caused the dropping oil pressure with RPM initially. Maybe when you added the engine flush, it clean it out some which allows the oil pressure to rise again with RPM.

The oil flush may have also cleaned out the sludge in the lifters and now the one tapping is just bleeding down too fast causing the tapping.