The federal government had super strict emission laws for vehicles starting in the 70s. This was before computers were cheap and reliable enough to stick in average vehicles, so the way automotive engineers got it to work was to have vacuum lines to send signals to the carburetor and distributor. They probably could've done it with analog electronics, but you already have a free source of vacuum (the intake manifold), and there isn't an simple way to convert an analog voltage to a linear position, while you can do that with a diaphragm and vacuum.
Thanks for illustrating the nightmare that three decades later will still roust me from a sound sleep. Back in my pro wrench days, I had to remove-and-replace the head on one of those Hondas. What should have taken an afternoon soon turned into a hellish day-and-a-half of squeezing a vacuum tester.
not 70s but my Mercedes 300TD from 1985 made extensive use of vacuum hoses to power lock doors, run pumps and even to turn off the engine (it's diesel so no spark plugs.) I think it was built that way because electronics were more expensive?
the engine was a marvel of engineering. I got it to 400K+ miles (odometer eventually broke), and I could drive just fine even after my alternator broke and I had no electrical power whatsoever. I also could (and did) do extensive maintenance myself because there were no computers to fiddle with and everything was modular.
> I think it was built that way because electronics were more expensive?
Mercedes has been the king of Rube Goldberg vehicle systems for ages. Anyone I know with one has had numerous electrical and other reliability issues. Shame as they used to make decent vehicles that actually lasted but boat anchored them with technological clown circus.
