I read last night what you where talking about. Thanks.  I learned that upon detecting a failure in the knock sensor (or infact knocking)  the controller should retard the timing a good 10 degrees.

This seems to fit the pattern of seing a sudden "retardation in the timing", and corresponding bad performance.   My knock sensor circuit is causing the problem.   I either have knocking or failure of the knock sensor - both could be either real or false detections. 

A question I ask now is - what explains that it happens only when I open the throttle more than say 10%m, at less than 3,000 rpm, engine hot or cold.

As I think about this, 'can some sort of misfiring  be falsly interpreted as knocking - or is the anti knock circuit smarter than that? (note I do not hear are misfirely during the retardation)

----- Original Message ----- 
  From: Kjmmensing@aol.com 
  To: McNock@easystreet.com 
  Sent: Friday, March 07, 2003 10:11 PM
  Subject: Re: sudden timing advance change/Tiico

  I am not sure. Is that (are all) TIICO 's OBDII? If so it will trip a code and go into limp mode (pre set timing and mixture) 
  It could be a problem with the computer 'receiving' the signal 
  I know VW had a few problems with knock sensors and had tech bulletins to retorque them. I think they were replacing connector pins also. 
  check all the grounds real good to.