preterite, imperfect, past and present participles
So far I understand that imperfect is used when setting a scene in the past, for emotions, dates/time, for things that happened habitually, something that is ongoing, or to say that something was happening when it was interrupted by another action (por ejemplo: Comíamos la cena cuando el ladron entró.) I understand preterite is used for those interrupting actions, to describe the start or end of something, happened only once or has a definite start and finish (except dates). I am definitely still fuzzy with these, but what's complicating things is adding in present participles (used in imperfect- such as: estaba manejando)... what's the difference between saying that and "manejaba"? And indicative + past participle. If a past action is ongoing- aren't I going to use the indicative (haber+ past participle?) When/why would I use imperfect an how does it change meaning?
I know there are several questions wrapped up in this, but they are definitely linked and I'm hoping to sort of crack the code on past tenses. Help!
Please take a look in the Reference section, which contains many articles about the Spanish past, future, etc.
So far I understand that imperfect is used when setting a scene in the past, for emotions
Setting a scene makes some sense, but emotions can be expressed in an tense (including preterite). Eg. Me sentí culpable.
...dates/time, for things that happened habitually
Dates and time if you are saying what was the time in some situation.
Habitual actions can be expressed in any tense. Eg. Fui todos los días. Imperfect can be interpreted as habitual if the context suggests that it is habitual. Eg. "Iba al trabajo... cuando me encontré con Pepe" is not habitual because "cuando me encontré con pepe" suggests that it was a single event around which the imperfect can be framed, but "El año pasado Iba al trabajo en bici", it is habitual because "El año pasado" clearly gives a wide time span for habitual actions to take place. The most likely way a native would interpret "El año pasado fui al trabajo en bici", without further information, is that I went to work by bike just once, but if we add more information and we say "El año pasado fui al trabajo en bici, pero este año voy en coche", the most likely interpretation for the preterite now would be habitual too. There is a serious misconception in the relationship between imperfect and habitual actions, even though they often go together.
something that is ongoing, or to say that something was happening when it was interrupted by another action (por ejemplo: Comíamos la cena cuando el ladron entró.)
Nothing wrong with that one.
I understand preterite is used for those interrupting actions, to describe the start or end of something, happened only once or has a definite start and finish (except dates)
Only once? "Fui al gimnasio 1500 veces." "Juan comió en el restaurante todos los días". The definite start and finish is fine.
adding in present participles (used in imperfect- such as: estaba manejando)... what's the difference between saying that and "manejaba"?
That will take a while to explain, but a starting point is that they are related to "manejo" and "estoy manejando", but in the past.
If a past action is ongoing- aren't I going to use the indicative (haber+ past participle?) When/why would I use imperfect an how does it change meaning?
The name of the tense haber + past participle is present participle in English, and pretérito perfecto in Spanish. This tense is more used in England and Spain than in USA and Latin America, but we use this tense when we want to express how this past event is relevant to us right now, or because it is a past even that has finished right now.
When/why would I use imperfect an how does it change meaning?
That's easy, because it is almost identical to the English counterpart. It describes past events that had finished before other past events. Eg. We had already eaten when you arrived. In Spanish is called pluperfect tense, and in English past perfect.
delete...better answer provided.
If I understand part of your question you are asking about the difference between:
Planchaba la ropa cuando el teléfono sonó.
Estaba planchando la ropa cuando el télfono sonó.
In this context there is little difference in meaning between the two. Either tells of an ongoing action at a moment in time in the past.
However, the imperfect in other contexts is used to express an ongoing action in the past that is habitual, or has no start, stop, or duration of the action is emphasized. It does not have to be painting a background when an interrupting action occurs. That is only a single context in which the imperfect is used.
María trababa en una oficina. When? Yesterday? Yesterday in the afternoon? Last year? For a day? For 10 years? No time period for the action is emphasized.
Maybe to help you understand the time aspect you would be better off asking about the difference between:
Estaba planchando and estuve planchando. (imperfect progressive vs preterite progressive)
Both refer to ongoing actions in the past that are interrupted, but the imperfect progress action is ongoing, while the preterite progressive action ends when the interruption occurs.
As for the rest of your question, I cannot follow it. I have no idea what the indicative+pp means?
Are you trying to contract the present perfect tense with imperfect past?
trabajaba (habitiual) vs. he trabajado??
For that I would suggest that you read Heidita's comments in previous articles discussing their usage in Spain. (in Spain it seems they are sometimes identical in usage and which tense is used is just a regional preference).
You might be interested in this article from Hispania [Publicaciones periódicas] Volume 78, Number 1, March 1995, in which Diana Frantzen discusses teaching in colleges and universities: Preterite/Imperfect Half-Truths: Problems with Spanish Textbook Rules for Usage.
Here the abstract:
Preterite/imperfect usage has the reputation of being one of the hardest grammatical features of Spanish to learn. While this is partly due to the fact that English does not indicate aspectual differences in the same way Spanish does, some of the blame lies with misleading textbook explanations which often are only half-truths, at best. A discussion of problematic P/I textbook explanations shows why the presentation of a more reliable, simpler set of principles serve as a preferable alternative to the problematic rules of thumb.
OK- I've had a brain flash... maybe.
Lazarus used the example: "Fui todos los días". Is the difference between that and "Iba todos los días" roughly like saying "I went each and every day" compared to "I used to go every day"???