Several years ago, when I was deeply involved with a controls engineer on my ultimately successful but economically unviable electronic Vacuum Sensor Device (VSD) replacement project, I learned the location of the partially hidden manifold takeoff that feeds the VSD. On my car, that line now feeds a repurposed Chrysler MAP sensor and then an electronic circuit that feeds the timing controller.
Today, while performing a thorough visual and wiggle test of the numerous plumbing bits that comprise our L-Jet systems, I pulled on the aforementioned vacuum line and...wait for it...it came off in my hand.
Trimmed it back 1/2", and reattached.
The engine struggled for a moment to fire, cleared its throat and settled into a stable idle. Good throttle response followed and it appears I'm back in business.
Still puzzeled however, since a vacuum leak at that point should have simply resulted in loss of ignition advance, with the timing ECM reverting to base mapping. Also, while a vacuum leak at that location would surely effect idle, when air requirements are low and critical, I don't believe it should have resulted in the abrupt engine cut out I experienced.
Many Spider owners have experienced leaky VSD's, with the primary symptom being a whistle from behind the passenger seat and, as the situation worsens, an increasingly ragged idle. Lack of vacuum advance due to a failed/failing VSD will also reduce performance somewhat (for those with sensitive seat-of-the-pants
) as well as marginally degrading fuel economy. A careful economy check with my electronic unit indicated about a 5mpg improvement at steady cruise over a 300 mile round trip (to 32mpg) on an essentially flat route, w/wo VSD. I'm at 4500' here in Northern Nevada and 90% of the journey was as close as possible to 60mph.
Back to my current situation, at throttle positions above idle
even a massive leak, and resultant unmetered air at the VSD fitting is not particularly significant, considering the total volume of air moving through the system, and again, I don't believe abrupt shut down should have happened.
Hey Eric! Maybe I did just run out of gas!
Thanks again, all! 👍