Nissan Repair: 87 Nissan P/U, valve lifter, haynes manual

Question
My 87 D21 with the Z24 engine, began "pinging" after a fuel fill-up.
I thought it was just poor quality gas since I had never used this station before.
At about 1/4 tank left, the engine began running/idling rough,
there is a moderate loss of power, but what has me most worried is that on acceleration, and almost all the time,except at no load, there is a noise like a very loud "ping" that follows engine speed, and seems more in line with a knock.
Have I got a rod issue, or is it more likely a valve/lifter type of problem?
The truck has 204,000 miles on it, the oil has been changed regularly, but it does have a small leak on the front seal that started a few months ago.
Please help.
Also, do you know of a website that might have exploded views of this engine?


Answer
Kenneth,

You might have a rod knock but since I cannot hear it I could not be for sure.  I would fill up with good gas and check the timing.  If there is a knock that follows the engine speed up and down then you have a problem.  I would purchase a Haynes manual for your pickup as I do not know of an on-line source for information for your year.  Nissan stops at 2000 on-line.