Get a car (mine arrived as a pile of junk on a flatbed), some tools, and start turning wrenches. It's not that hard, and I (and a couple friends) had a heluva good time. I suspect an account of that helped me get into engineering college.
My only regret is I ran across a '68 Chevy SS for $600 that I passed on.
I learned entirely by wrenching on my own car. Engine internals and transmissions are hard simply because you often need specialized tools. But there are plenty of parts you can fix yourself with only simple tools.
The main challenge now is that newer cars have a lot more complex components. Back in the '70s you could completely disassemble and refurbish a carburator. Fuel injection systems are a lot more complex. However, a lot of the systems on newer cars are still pretty basic.
One of the benefits of knowing how to work on cars is saving money. I fixed my wifes car (emissions failure) with a $12 part from ebay when a garage wanted $150 just to diagnose. And if you do have a garage work on your car, explaining what's wrong in way that makes you sound knowledgeable goes a long way to prevent being ripped off.
All you need is the ability to read, the desire to learn, the courage to get your hands dirty and not be afraid of breaking things, and some mechanical aptitude. And a little money to spend at Harbor Freight for some tools.
What's weird is my wife actually managed to get the car restarted after a while, and drove home that way!! It was making a terrible tapping noise though. I'm not sure how it was running that way; I didn't investigate too closely. This was a 2000 Acura Integra GS-R, by the way.
Anyway, I left everything alone in the other 3 cylinders because that all looked fine, and I replaced the piston, rod, and journal bearings on the bent one. I also replaced all 4 valves. It wasn't really that hard; I took the head and new valves and valve seals to a shop that specialized in rebuilding cylinder heads and they cleaned it up (it already had close to 100k miles at that point, so there was a lot of carbon build-up) and replaced the valves. They also put together the piston and con-rod for me as I didn't have a press for that. Then I just did the standard bore honing and put it all back together (and cleaned up the domes of the other pistons while I was at it). Worked great after that. The total cost wasn't much either; the bare parts only came out to a few hundred IIRC, from one of those online OEM parts sellers, and the shop work was $250 IIRC. The only specialized tools I needed were torque wrenches (which you should have anyway, but they're absolutely critical for engine work), and an air impact wrench (the crankshaft pulley bolt on that car was a real bear), and a drill-operated bore hone (cheap).
The manual showed a picture of a guy using a foot long breaker bar. What a joke.
I have a breaker bar, but I haven't used it ever since I got an impact wrench. You can put a lot more torque on a bolt with a handheld impact wrench than you can with a giant breaker bar; they're really a quite remarkable invention when you think about it. The one I have (1/2in drive Ingersoll-Rand titanium body) has 1000 ft-lb IIRC.
I have removed every rolling part of my ATV. It's quite strange to go 65MPH knowing that you put all the parts together... I am still alive so far, ha. :)
I am all about finding the original parts that the dealer will sell, but on the aftermarket at reasonable prices.
What still troubles me is passing my bi-annual smog checks. It's not just my vechicle, it's family members vechicles.
I can check most of the smog components, except the catalytic converter.(I found away around checking the catalytic converter, but won't divulge, because it might be illegial.)
The one tool I might buy if the price was reasonable is a device that measures the emmissions out of the tailpipe. I think there's a big need for portable emmission testers. The price point would need to be around $300 for my taste. I don't know if it's even possible at that price point? I'm basically just concerned with HC's.
In order to pass emmission standards, I make sure the engine is running reasonably well. I change the oil. I check all ERG. I make sure that cat is hot. I then check the voltage off one of the O2 sensors(gotta pick the right on, and be quick with the voltage measurement. The computer will throw things off pretty quick with the wrong O2 sensor dissabled.) With the 0-5 volts you read you can get a good idea of the stoichiometric burn of the gasses. You can detect wether the vechicle is running rich, or lean, but it's not fool proof.
Even with preparation, it's hit it miss whether a vechicle passes smog.
I would love to gave a home devise that measured these gasses.
I'll pass this along. All Smog shops are in CA are required to have onsite one Emission manual to show the customer.
Good shops have two references. They look at this information when they do the visual examination. Good shops usuall have Motor Emmissions for the current year, and a subscription to Mitchell Manuals. A subscription to Mitchell manuals(OnDemand5) is more money than the Motor Emission publication, but it's hardly ever Wrong.
If you fail the visual on a smog test, ask to see the refrence material they used to fail you. If it's a Motor Publication--the information might be wrong. It's filled with many errors. Most shops cheap it out and only buying the cheaper Emission manual. The Motor Emission manual is joked about among Smog Techs. They know it's filled with errors.
I kinda went on, but frustrated from dealing with a recent smog check.
When you say the "right" O2 sensor I presume you're talking about the one after the cat? Doesn't that mainly tell you whether the cat is working or not? If the engine is running a bit rich and there is a bit of excess fuel coming into the cat, the cat should burn it up, I think.
And you probably know this, but there is an important difference in the voltage readings depending on whether you have wide- or narrow-band O2 sensors. Wideband is typically for performance cars.
$30 is way too expensive btw. On aliexpress i bought a wifi (because of iphone) dongle for $9,99 incl shipment.
Plus it just looks more like an Apple product and less like their mom's shitty Camry they grew up being to school in.
Lexus has been known to make things deliberately difficult to reach, like putting the starter motor in a place where getting to it involves disassembling most of what's on top of the engine (requiring the replacement of lots of auxillary "soft" parts like gaskets and o-rings in the process):
http://www.lextreme.com/starter.html
In comparison, most other makes and models mount the starter motor somewhere on the side of the engine or transmission where getting to it doesn't require disassembling much else.
PS - I drove a manual transmission Mazda truck that had no starter for 8 months. Thankfully, I live in a mountainous region, so "push starting" the vehicle by using a hill was "easy" (except when it wasn't).
I found I can't even rotate the tires on my current car (Sonata) because it's got no central jack point. Seems to be designed just for shops that can lift all 4 jack points at once. :-(
Most engine covers pop off without even using any tools.
Parts are still readily available, though anything that moves under its own power is likely to sell for more than it did new (which wasn't much in today's dollars). But you'll get smiles and waves anywhere you go whether you end up in a Bug or a Bus.