Hello. I've got a 1990 Nissan Pickup 2WD with a 1989 2.4 liter 4
cylinder 2400 12 Valve Engine. Everytime I crank the vehicle, whether
it be hot or cold, it seems to rattle for about 6 or 7 seconds until
the oil light goes out. After that the engine runs smoothly with no
problems whatsoever. I recently changed the oil pump and it helped
reduce the problem slightly. I've been trying to figure out what the
problem is. I've changed the oil and put heavier grade oils in it. I
was using Castrol Synthetic 20W-50 until I replaced the oil pump and
now I'm using Castrol GTX 20W-50. I've also been using a Fram oil
filter everytime I've replaced the oil. I've had no other problems out
of the truck other than that rattling when I crank it up. Usually when
it's only been sitting for about 30 minutes or so it cranks up with no
rattling, but if it sits for 2 or more hours it has the problem. I've
been told to try these methods:
Replace PCV Valve
Replace Lifters
Add Slick 50 my next oil change
Remove the oil pan and change the oil pickup tube
Add Engine Restore
Replace the Head

Of course I want to try the easiest (and cheapest due to being a
college student living on campus) way to fix my engine because I know
that rattling sound over time can probably become an even worse
problem than it already is. I've had people tell me that it's normal
for it to make that sound. I find it very hard to believe that it's
normal.

Thank you very much to anyone who responds,
Matthew