MAC11 help needed

[cody at 5000tq.com]

Yes that is true. I'd also like to point out that on an MC1/MAC-11 the  
knock sensor is very unlikely to cause any noticable running issues.  
The knock sensor system will only retard the timing to a maximum value  
(I don't know what it is) and at that time it lights the CEL if the  
knock persists (or the sensor says it does). I know that this won't  
cause running issues from when I was tuning my 500+hp 5000tq - I  
forced it into maximum retard a few times and the only ill effect was  
some way high EGT's.

I'll also add into that that the daily driver 5ktq has a bad sensor  
and trips the CEL on a regular basis with knock sensor codes  
(including the one that indicates that maximum ignition retard was  
reached), but the car runs great.

-Cody Forbes
http://www.5000tq.com


Quoting Nick Lawrence <nick at beol.net>:

> 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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