[V8] Who Works on ECUs?

[dsaad at icehouse.net]

I missed that fact. (sorry - not paying attention I guess...) So - my next test
would be to remove the plug to the ISV and see if anything changes. If not, the
ISV driver could be toast. If I remember, the ISV is designed so that it will
idle fast with no power to it.
Given that a different ECU does work, you have pretty much eliminated all other
external inputs and wiring.

On repairing your ECU, it may well be possible. It just depends on what they use
for a driver. If it is an off the shelf part, and the problem is not upstream of
the driver, it should not be that big a deal. Maybe you can take a good digital
picture of the inside of the ECU and note the part numbers of all the big power
transistor type devices? I have never been inside mine.
You should also be able to trace the ISV wire back into the box and to its
driver with an ohm meter.
You also might inspect all the solder joints around the ISV driver and connector
with a magnifing glass.


Dave


Quoting "Buchholz, Steven" <Steven.Buchholz at kla-tencor.com>:

> ... the fact remains that the behavior changes simply with the ECU swap.
> Perhaps a case can be made for a temp related idle difference, but it is
> still true that each ECU is seeing the same temp sender.  Personally, I can't
> see a connection between an OXS and idle speed.
>
> Steve B
> San José, CA (USA)
> >
> > My thought as well - the ECU would not idle this high unless maybe it
> thought
> > the engine temp was below zero F?? even then I doubt it, and you would
> also
> > have a very rich mixture.
> >
> > Most likely you have a major air leak or the throttle linkage is binding.
> > There are a few known trouble spots. I would pull the throttle body off
> (not
> > hard to do, but there are some rubber gaskets that could break) and
> inspect
> > thoroughly. There are lots of bearings and bushings to get sticky.
> >
> > Dave
> >
> >
> > Quoting Ingo Rautenberg <i.rautenberg at waratap.com>:
> >
> > > See, I still see a problem.  You shouldn't have a steady idle of 1100 to
> > 1200
> > > rpm (even with the auto ECU).  That is too high. Have you checked the O2
> > > sensor by unplugging it?  I've had sheared O2 wires that threw the O2
> values
> > > way out of wack trying to  get the engine to compensate.  Bad info in
> --
> > bad
> > > info out or something like that.  Last thing would be to check for
> jammed
> > > cruise control rod, with the bushing at the edge of failure.
> > >
> > > Best of luck.
> > >
> > > Ingo
> > >   ----- Original Message -----
> > >
> > >   We (yes, I sought professional help) have looked for and not found a
> > vacuum
> > > leak.  I think in this case the problem really is the computer, because
> on
> > > swapping in a computer from an automatic, the idle was consistently
> around
> > > 1100-1200 rpm with no trouble codes.  With my computer, it is down
> around
> > > 800-900 until it decides to be in the 2000-3000+ range--this typically
> > occurs
> > > when pulling up to a stop sign.  If it were a vacuum leak, I'd expect
> code
> > > 2231 saying that the output to the ISV is out of range.  The code we're
> > > seeing is 2111, and the manual mentions the possibility that the
> Motronic
> > > itself has a problem.
>
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