[ischmitz]

The two most likely culprits for intermittent operation on the 3.2 are the DME and the DME relay. Both are known to suffer from issues that "come and go"

If you have the next no-start issue make sure you have a known good DME relay in your glove box to exclude it as root cause. I am a little concerned that you previously swapped the DME relay and it did not solve the issue. Assuming that you installed a new DME relay and still had the no-start and then went back to the old relay only to find the car fired right up tells me both relays are O.K. and you most likely have something else going on. Just put the new relay in and make sure it runs on both. Then put the new relay away as the spare.

The sensors are more prone to failing under temperature. Cable issues are not very comon. To make matters worse there is some complex logic to the sensors:

You need the reference sensor to function at least for one pulse to get the engine started. After that the DME "occasionally" looks for the reference pulse to make sure timing is synched to TDC of the engine. The speed sensor signal is required at all times and that is what tells the DME when to fire the spark and injectors. An intermittent reference sensor is very hard to diagnose. As someone else mentioned there were some instances where an aftermarket flywheel didn't have the right material pin installed to trigger the reference sensor. To diagnose you can plug a spare sensor into the harness and wave a metal object in front of it. One pulse is enough to transition the DME into 'run' mode.

If either sensor is not present (disconnected, damaged) the engine will never start or even sputter. Not a single spark event will be issued and a single injection pulse will be issued. However, once the engine is running you could unplug the reference sensor and it would run on for a little bit.

If the engine doesn't start but the exhaust starts reeking of unburned fuel after several minutes of cranking you most likely have a bad DME (failed ignition stage). That failure can be very intermittent. One day it runs perfectly fine and the next it is dead as a doornail. Then all of a sudden it works again only to fail in the most inopportune moment. Sometimes it is just cutting out.

The only way to properly diagnose that is to disassemble the DME and inspect with a high-powered microscope for hairline cracks in the PCB.

Good luck,
Ingo