TBill

If you disconnect the idle switch the F.I. unit will never know when the 
throttle is closed, so it will dump in excess fuel when decelerating (less 
engine braking, certainly wasting gas and increasing emissions), and the idle 
stabilization won't work properly - so loading the engine (A/C, electrical 
loads, etc) will affect the idle speed.

The F.I. system responds to this switch both when decelerating (cuts out fuel 
injectors) and when coming off idle. The switch has to function at the correct 
"off idle" position or (according to Bentley):

if the gap is too large (switch acts too late) the engine will surge when 
coming off idle (The FI unit doesn't react until the throttle is too far open 
- then it will respond to the open throttle and jump to the higher RPM - 
skipping the lower RPM positions) - this sounds like your situation 

if the gap is too small (switch acts too soon) the engine will tend to cut out 
or stall coming off idle.

The Digijet (83-85) also has a full-throttle switch, and these models adjust 
differently than the Digifant (86-91) which only have the idle switch.

For the Digijet there is a small adjustment screw on the throttle arm that 
triggers the switch. Bentley says to adjust by first closing the throttle; 
then adjust the screw until the switch JUST closes; then turn the screw 
exactly one turn farther IN and seal it in position (nail polish?) 

The Digifant switch is adjusted by a cam and feeler gauge.

This does affect the behavior starting from idle a lot - and the car will 
react better when it is set properly.

Tom Brunson
Austin

Craig Rogers wrote:
> 
> Sounds like it could be the idle portion of the switch that you are talking
> about.  If that sticks and stays closed when the throttle is opened,  the
> engine will seem to hunt until it reaches a point where the deceleration
> fuel shut-off is bypassed at around 2500 RPM. Try adjusting it. Bentley
> covers it.

That sounds right,altho it ends up near 3000 rpm.  Adjust?  What's to
adjust?  It seems to work normally, makes a little click, but evidently
the circut stays open (or is it closed?)  Anyway, just yanked one of the
wires on back and it runs fine.  I don't have a Bently, hence all the
questions,ie,  WHAT IS IT?  And do I need it?  What for?

TBill