Simple answer (fun intended) > It Stabilizes the Idle ~ Keeps RPM & Smoothness Comfortable ~

The 1.9 & 2.1 Idle Stab’ Control are handled differently in that 

1.9 is strictly electronic control of Ignition Timing & Fuel Injector Open Duration

2.1 added the Idle Air Control Valve into the fun which is a pulsed valve that adds air as needed >

        mostly open under normal warmed up running conditions & closed for cold start ~

There are most likely some more sophisticated/accurate answers roaming around JerryVanWorld ~ 

> On 27 Jul , 2022, at 9:50 PM, Jeff Palmer <w.jeff.palmer@icloud.com> wrote:
> 
> So what exactly does the idle stabilizer do?  
> Jeff
> 
>> On Jul 27, 2022, at 9:06 PM, OlRivrRat <OlRivrRat@COMCAST.NET> wrote:
>> 
>>       I’m pretty darned sure that the reason that DHs prediction was correct is that if any 1 of the
>> 
>> sensors that the ECU gets data from for Fuel Management is disconnected the ECU will go into Open Loop
>> 
>> & ignore all or most Fuel Management Sensor Data ~
>> 
>>       Disclaimer > Not Absolutely sure due to 77Yr Old Brain ~
>> 
>> 	
>> 
>>> On 27 Jul , 2022, at 10:09 AM, Eric Caron <ericcaron96@COMCAST.NET> wrote:
>>> 
>>> Hi Dave,
>>> 
>>>      Sadly that is well known as a unlikely cure.  The sensor tested out fine.  But due to a needed muffler a new one went in.  It also tests out perfectly.
>>> 
>>> Interestingly, Dennis predicted this would be the case and that it would be something else in the system. 
>>> 
>>> It will be so interesting and satisfying to solve this mystery.
>>> 
>>> Keep the tips coming.
>>> 
>>> Eric Caron 
>>> 84 2.3 GW with 1.9 fuel management 
>>> 
>>> 
>>> 
>>>> On Jul 27, 2022, at 11:57 AM, David McNeely <davmcneely40@GMAIL.COM> wrote:
>>>> 
>>>> So if the problem only manifests itself with the O2 sensor plugged in, put
>>>> in a new O2 sensor.
>>>> 
>>>> On Wed, Jul 27, 2022 at 6:23 AM Eric Caron <ericcaron96@comcast.net> wrote:
>>>> 
>>>>> Hi collective mechanical mind.
>>>>> 
>>>>> Reporting back still not solved running issue on 2.3 with 1.9 fuel
>>>>> management.
>>>>> 
>>>>> Many steps still not done as friends are busy and summer is full of
>>>>> activities.
>>>>> 
>>>>> Issue is still.
>>>>> 
>>>>> Van idles high.
>>>>> Screw for idle control closed to max.
>>>>> Checked for vacuum leaks and not finding them.
>>>>> Tried to check timing but idle too high about 1,000 rpm and now and then a
>>>>> surge to 1,200 RPM .
>>>>> 
>>>>> Engine  stumbles only when O2 plugged in and engine warm.  From a stop
>>>>> press excellerator and 2 out of three times it will hesitate stumble or
>>>>> skip.  Then find itself and go.  No O2 and it seems fine.
>>>>> 
>>>>> Still need to try a friends ECU
>>>>> 
>>>>> I’m hoping to soon have most of a recently working 1.9 ignition system to
>>>>> have for testing and spares.  I know diagnostics is better but still having
>>>>> working spares will make maintaining the old system easier.
>>>>> 
>>>>> I don’t need it to be perfect but this skip and running rich needs to be
>>>>> resolved.
>>>>> 
>>>>> Other then this van is currently ready for a long distance trip.
>>>>> I recently discovered that a long term friend from bus events has a twin
>>>>> to my van, year, color, and even the engine and fuel management.  Currently
>>>>> enjoying a trip up and down the east coast.  This gives me hope for a good
>>>>> running van in the future.
>>>>> 
>>>>> Any additional tips are always appreciated.
>>>>> 
>>>>> Eric Caron
>>>>> 
>>>>> 84 GW 2.3 with 1.9 fuel management
>>>>> 
>