I'm with Ken. sounds like a vacuum leak.

Check the hose from the Crankcase vent on top of the engine over to the
AFM. These will rot out on the bottom and go un-noticed. Caused me all
kinds of idle grief until I found it.

John Rodgers
88 G:L Driver

Tabe Johnson wrote:
> Ken,
>
> Thanks for the idea.  Tried a new ECU; no change.  Still idles high.
>
>
> tabe
>
>
> --- Ken Wilford <kenwilfy@comcast.net> wrote:
>
>
>> I had a customers van here not too long ago with idling issues.  Of
>> course you need to check your grounds and the throttle position switch
>> first to see if these could be bad or out of adjustment.  If they are
>> fine then I usually swap over the idle computer from a good running
>> van.  If that doesn't work I swap over the valve on top of the engine.
>> Still bad?  I was scratching my head on this one, then I just tried
>> swapping over the engine ECU.  Idle went back to normal.  Apparently
>> something in the Engine Control Unit itself (under the back seat) was
>> causing the idle problem.  Just an idea.  I have all of these parts to
>> swap around so it makes it easier for me to test for these problems.
>> You could try swapping in an ECU from a good running van from 86-91
>> (they will all work) and see what happens.  I have rebuilt units with a
>> one year warranty for $250 if you find you need one.
>>
>> Just FYI:  The factory 2.1l ECUs had problems with three things.  They
>> decided to integrate the ignition module into the ECU so it got hotter
>> than the older ones with the separate ICM.  Then they stuck it under the
>> rear seat where it gets no air flow.  Then who ever was building the
>> boards decided to do a crappy solder job on several of the connections
>> (cold solder joints).  Murphy's law was in full effect that day!
>>
>> Hope this helps,
>> Ken Wilford
>> John 3:16
>> www.vanagain.com
>>
>> Tabe Johnson wrote:
>>
>>
>>> To recap:  Both my engine and that of Larry Himli (both 2.1s)
>>> idle around 2400-3000 rpm.  In my case, it used to be that it
>>> would just do that till it got warm, then it would idle properly,
>>> and sometimes pop up to idle at 2400-3000 rpm.  Now it does
>>> it all the time.  I swapped out the idle computer.  No change.
>>> My temporary  fix: Unplug the idle air bypass solenoid.  Engine
>>> runs great otherwise.
>>>
>>>
>>> Larry's AC thing is interesting -- it says that the idle computer
>>> is at least trying...  I'm still wondering about the
>>> computer.  There was a post a few years back about fixing damaged
>>> computers by replacing a one transistor that always blew.
>>>
>>> The inputs and outputs are pretty simple.  I went through this
>>> too, and heres what I came up with:
>>>
>>> IDLE COMPUTER INPUTS:
>>> Idle Switch
>>> PS Switch
>>> AC Switch
>>> Hall Generator
>>> Temp sensor 2
>>> Power from relay
>>>
>>> IDLE COMPUTER OUTPUTS:
>>> Idle air bypass
>>>
>>> Ideas?  Anyone?  Beuller?
>>>
>>>
>>>
>>> tabe johnson / 87 westy
>>>
>>> --- Larry Himli <lhimli@msn.com> wrote:
>>>
>>>
>>>
>>>
>>>> Bummer, I was so sure the relay would fix it....but no luck.  It still revs
>>>> up to about 2K and at least it oscillates back and forth.  I turned on the
>>>> air conditioning and it really revved up.  So now we have to try something
>>>> else.  Have you studied the wiring diagram?  I will try to look it over and
>>>> see what might feed the relay, etc.  At least it isn't raining
>>>>
>>>>
>>>>
>>>
>>>
>
>