MAC11 help needed

[Nick Lawrence]

Regarding knock sensors,   I have seen in writing that the knock sensor 
system only does it thing above 3000rpm.  Does anyone know positively if 
that is true?
I'd like to know.
Nick
----- Original Message ----- 
From: "Louis-Alain Richard" <laraa at sympatico.ca>
To: "'Rick Houck'" <rhouck at neo.rr.com>; "'John Lagnese'" 
<jlagnese at massed.net>; "'Quattro List'" <quattro at audifans.com>
Sent: Monday, September 01, 2008 11:28 PM
Subject: RE : MAC11 help needed


> If they are OK, then maybe something is triggering the knock sensor ?
> Something loose in the vicinity maybe ? One usual suspect is the vacuum 
> pump
> rod that is located in the head. I know an MC doesn't have one, it's a
> normally aspirated engine gizmo, but you may want to check for rattling 
> bits
> anyway.
>
> Then, timing tables are dependent of numerous sensors : RPM, manifold
> absolute pressure, intake air temperature, WOT and idle switches, and 
> knock
> sensor.  Did I forget something ?
>
> You said the erratic behaviour appeared after a rainy session, then maybe
> one sensor signal is impeached (corrosion, short, etc) and that signal is
> only processed after 2500 rpm, causing the rough running. You just have to
> find each sensor impact on timing retard to help you diagnose: guys with 
> MC
> knowledge should chime in here. Or guys with a Bentley for the MC...
>
> Finally, a few years ago, I had a similar problem on an Iron Duke engine 
> (GM
> 2.5 Litre OHV 4 cylinder for S-10/Sonoma). One mechanic took all of 2
> minutes to point his finger at the distributor reluctor, the round magnet
> that triggers the Hall effect sensor. It was originally press-fitted on 
> the
> dizzy shaft, but 10 years on, many small cracks had developed and the
> reluctor was free to move a few degrees around the shaft, causing the
> backfires. Replacement was the only solution.
>
> Hope this helps,
>
> Louis-Alain
> 1983 Quattro
>
>
>> -----Message d'origine-----
>>
> I have tried different torques on the original and spare knock
>> sensors with no change, but they are used, not new, but from decently
>> running cars.
>> Keep your thoughts coming.
>>
>> Rick
>
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