Toyota Repair: cold start lifter/spark knock/bearing noice, grade fuel, electronic timing

Question
My 1999 Toyota Tacoma 4ycl engine has what sounds like a spark knock when cold and under little load.The sound is louder when under maximun load. It doesn't happen when not under load. As the engine reaches normal operating temp there is no problem. Might it be a electronic timing problem?

Answer
Have you tried a different fuel supplier?
or jumpnig up to a "plus" grade fuel?
Maybe try some fuel cleaner in the gas tank.
If its pre-ignition as you suggest, it may be fuel quality related.
The knock sensor would prevent the engine ECU from making that much of a timing adjustment.

Keep in mind, I cant actually hear it.
Mike