Re: debugging the L-Jet

["Rich Wagner" <drsavage@domain.elided>]

Godfrey:

>New behaviors... When starting from cold, I find that the engine takes a
>little throttle to fire and then runs very roughly and slowly for just a
>moment before settling into a clean idle. Similar behavior when warm but
>briefer. Also, when it's good and hot, the idle will sometimes oscillate
>gently over a range of about 250 rpm and period of about 5-8 seconds. 
>
>Reviewing the manual and the Bosch injection book, this seems to me to be
>the auxiliary air device: either it's got a leak or the motor controlling
>the valve is getting funky.
>
>What do you think? It's easy enough to replace it but I would rather not
>spend the money for another gizmo if it's not the problem... 

The Auxiliary Air Device acts only to increase the effective throttle
opening, doing exactly the same thing that you do by slightly depressing
the accelerator.  About the only way it can affect the actual smoothness of
the engine at idle, is if the idle speed drops so low that the idle becomes
unstable.  That seems to happen at speeds below about 500 RPM.  With the
engine hot, the AAD should have no effect at all, except to cause a fast
idle if it's stuck open.  With the engine hot, unplug the AAD and start the
car.  If you still get the same roughness that goes away, the AAD is ruled
out.  Unless I'm not understanding your post correctly, I don't think the
AAD is your problem.  Keep looking.  Pulling a plug or two for a reading is
always advisable.  You need to determine what's going on inside before you
look for a culprit.  It's always illuminating to put a meter on the O2
sensor, too.  Provided you've got a good sensor, it's the easiest way to
see what's going on inside.