[s-cars] Diagnosing misfire cause

[Tom Rodriguez]

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