John seems to implying here that the idle stabilizer valve stops operating
once the Temp II sensor reaches operating temperature and passes off to the
oxygen sensor.  I had the impression that the idle stabilizer valve
continued to operate but would just back off its valve opening to the intake
thus reducing the idle and of course it opens back up when the A/C is turned
on or the power steering switch kicks in under load at idle.  So the
question is, should that idle stabilizer valve actually be off (not humming)
when warm up is completed and the A/C or power steering switch are not on?
If so, that's not what I'm getting as mine is always on.

Thoughts?

Jeff Warner
Galloway, OH

Date:    Wed, 14 Aug 2002 07:48:39 -0500
From:    John Rodgers <j_rodgers@CHARTER.NET>
Subject: Re: Engine start-up trouble

John

 The problem is most likely related to the Idle Stabilizer Valve (ISV)
circuit.
The stabilizer valve operates when the engine is cold to keep the engine
from
dying. Once the engine is warm, and the ECU gets a "warm" signal from the
Temp
II sensor, the idle stabilizer is isolated from the circuit. The engine
should
idle smoothly at that point.

Try removing and cleaning it with some carb cleaner. Also remove and reseat
the
Idle Stabilizer Control ( a box located behind the right tail-light - remove
the light housing to get to it). This action will help by removing any
slight
corrosion that may have occured over time.

The ISV should hum and you should feel a slight vibration when it is
operating.

John Rodgers
88 GL Driver

john Runberg wrote:

> Can anyone help me diagnose this?
>
> When I start my 90 bus in the morning it wants to run really rough - no
> power, hesitates, etc... Exhaust seems to have moisture in it and it
leaves
> a slight damp mark on the pavement. If I let it idle for a few minutes it
> runs OK (after the OX sensor has kicked in?). Once it's moving it runs
> great. If I start it in the afternoon it doesn't seem to exhibit the same
> behavior. Odd.
>