1989 Audi 90 Q rough Idle

[Anthony Attard <ACA@nrc.gov>]

Hello Audi fans.

I  have an idle problem with my 1989 Audi 90 Q.  It idles at about 850 to 900 revs.
OK, but it feels like it is missing every now and then.  The problem is not bad
enough to stall the engine, but it is not as smooth as it used to be before the
problem appeared out of nowhere, (or so it seems).  I have already replaced the 
idle stabilizer valve, so I know that my problem is not the idling speed, but rather
the roughness of the idle.  I have used a couple of bottles of ChevronTehron,
thinking it may be dirty injectors.  It helped a wee bit, but not much.  I have
replaced the air filter, plugs and distributor cap and rotor button, but not the spark
plug leads.  Could the spark plug leads be the problem??   The engine accelerates
well, stationary and under load.  I am baffled.  


I know this is long winded guys, but no suggestions is turned down.  
Thanks a lot.

Tony .    1983 Audi Q Turbo
               1986  4000 CS Q
               1989 Audi 90 Q