[V8] Idle Problem Returns to The Twilight Zone

[urq]

... thought I'd reported it here before ...

I can't speak to the automatic case, but I can tell you that a 5-speed runs 
just fine with an ECU from an automatic car.  I can also say that an 
"automatic" engine runs fine in a five speed with the 5-speed brain ... 
AFAIK there are no connections between the IC and ECU that the 5-speed ECU 
cares about.

It does seem a bit odd that the good whack cured the problem ... the only 
part that is socketed in the ECU (as I recall) is the EPROM itself ... even 
the board to board interconnects are hard wired.

I have not saved the EPROM code from an automatic car ... but I do have a 
copy of the EPROM and can read it in if needed.  I have soft copies of the 
contents of the 5-speed EPROM ...

I can also speak to the IC situation ... before I knew any better I bought a 
car that had an automatic cluster installed ... it worked just fine ... just 
the PRNDL display was lit.  Later I removed the back lights, and even though 
the LCD elements are all still visible in some lighting conditions, it isn't 
very noticable ... the only thing that is odd is that when I connected up 
the MIL wire, the incorrect indicator illuminates on the cluster ... not 
sure if this is due solely to the fact that this is an automatic cluster or 
something else.  I picked up a 5-speed cluster (I'd almost bet these will be 
rarer than ECUs!) which had a cracked bezel.  I've removed a bezel from an 
AT cluster and will glue it on my 5-speed IC when I figure out how to polish 
out the scratch I made removing it ... :-( ... The plan is to swap the 
speedo between clusters when I do the overall swap ... that way the mileage 
will not change ...

... final comment ... there is no "resolder fix" for these ICs ... I suppose 
an application of solder would definitely cure the interconnection problems 
... but it would render it impossible to disassemble in the future (but 
then, I suppose I might never misbehave again :) ... the fix that I use is 
to use DeoxIt (or equiv) on the internal connections ...

Steve B
San Jose, CA (USA)

>
> My WAG is that the ECUs are identical except for the EEPROM chip.
> It is possible that there other electronic parts included/deleted based on 
> the
> transmission type, but the circuit board is most likely the same.
> That being the case, an automatic ECU should be just fine in a manual car 
> as
> long as you swap the EEPROM.
> This could be confirmed by carefull inspection of the circuit boards. The 
> fine
> folks at IA would probably also know the answer to this.
>
> btw, I wonder if anyone has saved a copy of the EEPROM data for both auto 
> and
> 5-speed boxes?
> That would be a smart thing to do so we can re-purpose ECUs. As time goes 
> on,
> these things are going to get even harder to come by.
>
>>
>> I'm hanging onto the other ECU just in case.  There's a chance that both
>> computers have the same problem, but that seems unlikely.  Because some 
>> of
>> the signals to the Motronic come from the IC, I wonder if there's 
>> something
>> going on there.  Any differences between the 5-speed and automatic 
>> clusters,
>> apart from the speedo constant?  I'd like to have spare parts or at least 
>> a
>> chance of getting them before attempting the resolder fix.