Oil cap off kills car

[PMStaples@aol.com]

I have a 1988 90 Quattro, non turbo,10 valve, 5 speed. I am getting a rattle,
knock from the engine at idle, low speeds. The car seems to run OK, but not
great. While looking under the hood with the engine on, I took of the oil fill
cap, and the engine died immediately. Tried several times, engine cold, normal
temp same results. I checked the manual about the knock senser, and will try
to check out the wiring and timing today, but the engine dying has me
baffeled.
Any suggestion are appreciated. This group has a tremendous wealth of
information in it, although I do not often have the time to read all of the
daily posts, I am glad the Quattro digest is out there.
Patrick Staples
88 90Q
87 900T
87 740T