At 09:34 AM 3/17/2011, Rocket J Squirrel wrote:
>I want to emphasize that the hunting first appeared a couple years
>ago, that the hunting is sporadic but occurring more frequently now,
>and it occurs whether or not the idle stab thingy is connected or bypassed.

What's the rpm range?  Cycle time?  Does it correspond with O2 sensor
flip-flops?  Does it go away with the sensor out of the system?  Do
you have access to a spare ECU?*  Have you wiggled the heater
crossover pipe to check for a pulled-out stud (mine was the single on
the right side; I fixed it with some sensor-safe RTV under some thin
aluminum, with a hose clamp around the intake tube and pipe foot).

*I wish I had a p-code or block diagram description of the ECU code
but I don't, and don't have a good feel for exactly what it's
doing.  I don't have a strict rational reason to suspect the ECU
here, except that I always suspect the ECU when there's an
engine-control issue.  On the 1.9l the ECU only handles fuel control
- ignition timing is by a conventional distributor with centrifugal
and vacuum advance and vacuum retard, modified by electronic advance
from the idle stab module at idle rpm.  Idle compensation for power
steering and air conditioning is by valves that admit extra air,
equivalent to opening the throttle slightly.  Cold idle speed is
raised by a temperature-controlled air valve containing a
heater.  Its initial amount of opening is controlled by ambient temp
- I think it's fully open by about 0F.

Yrs,
d