# 4th Cylinder won't fire? 1993 Audi S4 UrS4



## digitaldub (Jan 17, 2003)

Hey Guys, 
I’m having a problem trying to figure out why the 4th cylinder on my 1993 Audi S4 (UrS4) wont fire? I will begin with a brief overview of the cars modifications, followed by an explanation of my diagnostics and the findings. Hopefully with that information in hand someone will point me in the right direction to locate the root cause of this issue.

The motor itself is modified with an MTM chip, RS2 manifold, RS2 turbo w/ upgraded wastegate spring, green top injectors, Samco Boost host kit with T-clamps. The car has not thrown ANY codes to let me know that there is an issue.
What I have already discovered:
*Started the car and all of a sudden engine felt like a diesel; very heavy with vibration – initial thought was I lost an ignition coil or spark plug.
*Checked and tested all spark plugs - all plugs work fine and still no spark to the 4th Cyl.
*Replaced the 4th Cyl Ignition coil with a new unit – Still no spark to the 4th Cyl.
*Replaced one of the two Ignition Control Modules – Still no spark.
*Swapped the other Ignition Control Module with the Ignition Control Module I just took off from the other side (I could only get my hands on one module as the dealer only had one on hand, and I wasn’t sure if both needed to be replaced.) – Still no spark.
*At this point I tested, using an amp meter, both cables running from the newly soldered Ignition coil to the two harness connector clips. – Both showed that there was a current going through them. 
*I now tested, using a voltage testing screwdriver (the one with the cable and light inside) to see if there was a current coming from the two white connector clips, located inline against the firewall, that one of the two ignition cables runs two. - Only two of the three terminals worked on each white connector clip.
My conclusion at this point is that there may possibly be a damaged/ burnt wire in the harness going from the white connector clips to the ECU. 
Can anyone shine light on this situation for me or possibly provide a picture/scan of the wiring harness layout from a tech. manual? I appreciate your time and thank you in advance.


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## URSledgehammer (Oct 3, 2008)

*Re: 4th Cylinder won't fire? 1993 Audi S4 UrS4 (digitaldub)*

This is like an enigma wrapped in a riddle. Everytime I read your post I think something else. Sorry I am no help.


_Modified by URSledgehammer at 12:09 PM 5-4-2010_


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