Re: I like my chips
I once experimented on an old big-block Ford LTD (429) by modifying the carburator such that it idled on 4 cylinders, on the mains (idle jets were closed off). Since half the cylinders got NO fuel, essentially, it needed regular fuel flow (not idle jets) to idle and do city driving. Gas mileage was significantly better, though I could not measure it other than noting how less often I had to put gas in. Highway mileage went up by about 20% though. And the car stopped "coughing" and running after I shut it off.
This is not a new idea, and maybe a car computer could alternate cylinders around on a modern engine to accomplish the same thing with EFI (just rotate which half of the cylinders get fuel) once the engine warms up. Or if you wanna tinker in your garage with a 40+ year old car that stlil runs, go for it.
As for engine trouble, the ODB-II (or later I guess) stuff usually tells you exactly what went wrong. But some time ago I had to step in to get the diverter valve assembly replaced on my current vehicle. It was building up water in an electric air pump (smog device) and causing it to fail, within the warranty period. I was tired if it failing and so I thought about it, did some online study, and determined that the diverter valve was leaking back into the air pump, and as a huge amount of car exhaust is water vapor, condensing inside the air pump and making it fail.
I figure if you can troubleshoot I.T. problems, you can use the same know-how and online earch ability to at least assist the mechanics with fixing your ride. (But I like the "ask a question" method so they do not get pissed at you doing their job for them - "What would happen if THIS component were to fail? Would it XX and YY and cause THIS to happen? Can we try fixing ZZ to see if it helps? I bet there's something wrong with it.")