could/could have/to be able to

I am trying to figure out a few things about these three could/could have/to be able to as I don't understand some things. In the grammar book by M. Swan it is written that:

1
Could (in the past) - conveys a general ability to do something within a long period of time
When I was young I could ride a horse.
Able to - means that something was done in a certain situation
I was able to ride a horse yesterday.

So, according to M. Swan it's not right to say:
I could ride a horse yesterday.

But I hear native speakers say things like

I could do it yesterday.
I could start the engine yesterday but I can't do it today.

Is it a mistake to say that provided we comply with Swan's rules or does it mean something else? Shouldn't it be:

I was able to do it yesterday.
I was able to start the engine yesterday but I can't do it today.
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2 Some people say that
"I could do it yesterday" - means possibility but not the ability.

So "I could do it yesterday" means: "I had an opportunity to do it yesterday."
Well, in this case I wonder what is the difference between:
I could do it yesterday
I could have done it yesterday.
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3 Native speakers say that:

I could do it yesterday, but I didn't want to. - is wrong.
It should be
I could have done it yesterday, but I didn't want to.

Then I don't understand why
I could start the engine yesterday. - is correct
It should also be
I could have started the engine yesterday.