2111 code....check engine light

[Doyt W. Echelberger]

Well, thanks all for the suggestions. In addition to listening to 
everything very closely, I put 20 ounces of Techron injector cleaner in 
with 3/4 tank of 93 octane and drove it for about half an hour in third 
gear at around 5k RPM, which was about 65 mph.

Then I tested it out a little differently by driving normally around town 
and in the country, and the check engine light almost never came on when I 
accelerated.  Not totally gone but BIG improvement. And the few times it 
showed up was when I only nudged up the speed rather than punching it hard.

So, if it is a faulty speed sensor, then that sensor normally plays a role 
in  enriching the mixture for mild acceleration of the sort that doesn't 
trigger WOT.  Because now WOT doesn't bring on the knocking that started 
off this thread. It did at first, right after I drove out of the shop, but 
as I blew away the carbon, the knock tendency became less and less.

And that's what I accomplished today.

Tomorrow I'll see if the injectors are even more capable, after sitting 
overnight in a bath of Techron-laced fuel.  And, I'll start looking around 
for a speed sensor that tests out around 1000 ohms. Anybody got one they 
want to get rid of?

Doyt Echelberger
still messing about with senior Audis