Join Date: Jun 2016
Location: Santa Barbara, CA
I have been following this thread from the beginning, and have even offered some suggestions, but I stopped once I realized that it seemed to be futile. I suppose could re-read the entire thread, and maybe I would discover a hidden clue that would suggest what to test next, but I am leery of sending you down a rabbit hole that results in another weekend of frustration and pulling your hair out.
I think that this thread proves that internet help can only go so far (not that there have not been lots of good suggestions), because none of the responders can actually see and hear the car, and it is why I refuse to diagnose any customer cars over the phone, even when I am 99.9% sure what the problem is. It seems like you have gotten to the point where you should take the car to a professional shop that is proficient in Bosch fuel injection (does NOT have to be an Italian car specialist). Now, finding a German car specialist or Bosch Service Center that is willing to take on an Alfa GTV6 is another story, but you never know.
You keep stating that it would cost $2,000 just to diagnose what is wrong---if there is a shop telling you this, that means they don't want to work on your car. Sure, the eventual repair could easily cost $2,000, but it's not like your car is only stalling once every 500 miles---because your symptoms seem to be chronic and repeatable, a competent shop with professional test equipment would likely figure out what is wrong within a few hours. If I weren't able to figure out a similar issue with one of my customer's cars after $2,000 worth of labor (even here at Santa Barbara labor rates), I'd consider quitting my job and do something else; this is not to say that I haven't had my share of problem cars over the years, but we certainly wouldn't charge a customer an exorbitant amount of labor if we could not solve an obvious issue.
I hate to sound cruel, but Bosch L-Jet is not rocket science, and none of the components of the GTV6 injection or ignition system are unique to Alfa or Italian cars. Once all of the various Alfa-specific voltage drop issues are taken care of, it is a matter of knowing how the system works and what to test.
Of course, aftermarket wiring and modifications to a 35+ year-old can muddy the waters, and it sounds like your situation is further complicated by the fact that you (at least somewhat) converted the ignition system to the later version, and seem to have other underlying issues as well. But even then, a sharp technician with a good DSO and multimeter and a 5-gas analyzer should at least be able to figure out the reason for the stumbling/stalling fairly quickly.
Please don't take this post the wrong way. I admire your persistence and fortitude, especially because it sounds like you work hard and have a family to support. But at some point, I think you have to throw in the towel.
I should be in Austin in mid-September to visit my sister and nephew who live there and to see the AMLS race at COTA. If you somehow still have the car then and it's still acting up, I'll happily volunteer a couple of hours of my time to at least determine what is going on.
Chris A: '81 GTV6 rescued from junkyard, "GT" car/'86 Porsche 944 Turbo track/street car/'73 BMW 2002tii fun street car/'74 Jensen Healey Lemons Rally car!