I have an 88 when I got it the owner said, it had a rod knocking,I told him since oil pressure would come and go away it was probaly a clogged pick up from lack of oil changes.I pulled the oil pan,pick-up, and valve covers and cleaned them.On start up I had oil pressure but a lot of lifter noise.I put a Quart of trans fluid in it and ran it,after about 20 minutes the lifters quitened down.I changed the oil and so for so good. I worked at an Isuzu dealer in 94-97.They were famous for noise lifters for lack of oil changes.It is what we would try before changing lifters,It worked a lot of times.Carl