[s-cars] Diagnosing misfire cause

[Cody Forbes]

The simple test would be with a logic probe (LED test light) on the input to the POS. If the ECU is bad it wouldn't be outputting a signal to the POS. If there's a signal going into but not out of the POS then that's the issue. This same testing could be done with an oscilloscope.

-Cody Forbes (mobile)

> On Jan 21, 2016, at 11:19 AM, manuelsanchez at starpower.net wrote:
> 
> Tom,
> 
> I'm curious, what were the shops test results and/or how did they determine that the ECU Ignition Module was at fault.
> 
> I'm just hoping to store this nugget of info for when "my time" comes around.
> 
> Thanks.
> 
> Manny
> 
> 95.5 urS6 Avant (RS2'd)
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Wed, 20 Jan 2016 18:39:35 -0500
> From: "Tom Rodriguez" <trodri69 at gmail.com>
> To: <s-car-list at audifans.com>
> Subject: Re: [s-cars] Diagnosing misfire cause
> Message-ID: <006501d153db$d2fb68d0$78f23a70$@gmail.com>
> Content-Type: text/plain;        charset="us-ascii"
> 
> Folks,
> 
>  
> 
> My shop has traced the misfire to a faulty DME Ignition Module.  This is a
> Bosch Motronic unit, part no. 4A0907551AA.  Audi wants $2,500 for a new one.
> Any suggestions on where to get this part for less money?
> 
>  
> 
> Thanks a bunch,
> 
>  
> 
> Tom
> 
>  
> 
> Tom Rodriguez
> 
> '95 S6, 267k miles
> 
>  
> 
> l engine speeds and
> under all levels of acceleration & boost, including at idle.  On some days
> the car starts well and runs well for a while, then begins misfiring once
> warm.  On other days it misfires when cold, and then clears up once warm.
> 
> 
> 
> I've read the technical advice provided at SJM Autotechnik on this subject,
> which points to either a bad ignition coil, a bad POS, or a bad fuel
> injector.  They also mention dirty plugs but mine look fine.
> 
> 
> 
> My problem is that every time I try to diagnose the cause, the engine
> refuses to misfire.  When it does misfire, I am not in a place where I can
> do any diagnostics.  It's very frustrating.  I'm hesitant to drive the car
> any long distances until I figure this out.
> 
> 
> 
> Thanks for any advice,
> 
> 
> 
> Tom
> 
> 
> 
> Tom Rodriguez
> 
> '95 S6, 267k miles
> 
> 
> 
> 
> 
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