[s-cars] Diagnosing misfire cause

[Tom Green]

Tom,

Your problems with an intermittent misfire are typical of what other owners experience with ignition problems.  The others seem to be able to take the time to do the simple diagnostics to find if there is one cylinder that is misfiring so the repair efforts can be concentrated on that area.  Not much advice you can get online if you can’t do that simple part.

Now you are stuck with a diagnosis of ECU death since the ignition module is not available for a repair of your ECU.
This could be a valid diagnosis since ignition module failures do occur, but I would encourage you to investigate further since a shorting coil or wiring could initiate the failure.  The forum on Quattroworld.com has an extensive FAQ section as well as many current threads on problems with these vehicles.  You may need to sort through a lot of chaff, but the information is worth the effort, and you can likely find a source for a used ECU if needed.  Where do  you live?  You may find a repair shop that has extensive experience with this ECU in the FAQ or forum also.

As far as Cody’s recommendation, I have never heard of Programma Inc ever completing a repair on the ECU for this vehicle.  Although they do list some vehicles with Motronic computers, they don’t include the UrS4/6 or any Audi vehicles in their expertise or inventory.  

For Cody:  Do these 30 repair jobs you mention in your recommendation include any 4A0 907 551 AA Motronic units
that were successfully repaired at this shop?  

Tom
’95 S6, 95.5 S6 avant


> On Jan 20, 2016, at 7:03 PM,  Cody Forbes <cody at 5000tq.com> wrote:
> 
> PS. Several places can also repair them. I highly recommend Programma Inc in 
> Florida, they have done probably 30 of them for me.
> 
> Cody Forbes
> Black Forest Racing
> (704) 489-0741
> www.BlackForestRacing.com
> Facebook | Instagram | YouTube
> 
> -----Original Message----- 
> From: Tom Rodriguez
> Sent: Wednesday, January 20, 2016 6:39 PM
> To: s-car-list at audifans.com
> Subject: Re: [s-cars] Diagnosing misfire cause
> 
> 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
> 
> 
> 
> From: Tom Rodriguez [mailto:trodri69 at gmail.com]
> Sent: Wednesday, December 30, 2015 6:32 PM
> To: s-car-list at audifans.com
> Subject: Diagnosing misfire cause

> Folks,
> 
> My '95 S6 is misfiring intermittently and I am trying to determine the
> cause.  When it misfires, it does so constantly at all 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