Re: Idle fluctuation

[jdouglas@mitre.org (jason douglas)]

>     I have an '87 4000q and have a question concerning idling.  When I 
>     come to a stop the car almost quits running.  The idle drops way down 
>     and just before it stalls it picks back up and idles just below 
>     1000rpm.  It does this frequently, but not always.
>     
>     Any suggestions?

as always, you should always make sure that the car is in reasonable basic
tune first.  if  you are getting reasonable performance and fuel economy
(i.e., the only problem is at idle), then chances are that you have proper
mixture, spark and timing.  you still, however, could have an improperly set
idle level.  on the bosch systems with which I am familiar, idle is a screw
that changes the effective size of a "circuit" that bypasses the throttle
plate.  I had a rabbit with this screw set to provide too little idle air (&
therefore fuel).  the symptoms were that it ran well, but the idle speed
would drop to perilous levels before a relay would cut in and add more fuel
(i don't recall what relay that was).  the result was an oscillating idle
speed, with the lowest speed in the cycle low enough for the oil pressure
light to come on.  yuck.

i had a similar problem with my 86 5000 - the idle speed sometimes dropped
way down before
stabilizing.  the culprit again was improper basic settings (idle & mixture).
------------------------------------------------------
Jason Douglas
MTS Dept G057                        
MITRE Corporation