engine knock ---why?

[Andrei Kogan <abk@phy.duke.edu>]

Hello,

The next thing on my list of things to address is this weird problem which
only happens occasionally. The engine in question is a 10v in our 90q. I
just got the check light working (the bulb legs were broken off) so I
finally managed to pull of the codes.

The problem: *occasionally*, the car would ping (knock, detonate) under 3/4
open throttle, mostly in 3d and higher gears. I don't get the check light
when that happens, 

Here is the puzzle :

if I floor it when this happens, the pinging goes away. At the same time,
the check engine light comes on, and stays on until I let off the
accelerator. This is consistent whenever the ping occurs.

The two error codes that I got point at the full throttle switch and the
coolant temperature sensor. Nothing about the knock sensor system or
ignition timing.

Question:

1. Could someone describe possible causes for the knock, besides the
ignition advance being too high. Does lean/rich mixture increase the
chances of knocking?  What about intake vacuum leaks ( which I don't think
I have, but you never know)

2. Is it possible that the err codes I get have anything to do with it, and
if  so, how?
3. How would you start troubleshooting it?

This will be my second exercise in cis maintenance, after fixing the isv
hose, so the experience is zero and any suggestions are greatly appreciated.

Andrei