I'm not sure what you mean when you say you've written numerous second novels. If they're written, why aren't they on editors desks?
The agent's job is not to love or hate your ideas. The agent's job is to sell whatever you give her to sell.
Other than this, stop giving up when you hit chapter three. Finishing a novel is no mystery. You stick with the one you start until it's finished.
Novels do not die around chapter three, writers simply stop writing them around chapter three, and move on to something they think is better. It never is, and leads to the exact problem you now have.
Just pick one, finish the damned thing, and send it to your agent.
Such a misguided little ray of sunshine you are, James. Seriously. And, you're completely out of whack on this response. Try reading the OP first before you decide to stomp all over it with your absolutisms that are two decades out of date.
Now, on to the OP.
First, stop trying so hard to write that "second novel." That's not what you're supposed to be doing. You're supposed to be telling a story and that doesn't include stopping in the middle of the process and telling yourself, "Oh, gee--this isn't a good
second novel." No.
GET THE STORY DOWN ON PAPER. THEN GO BACK AND SHAPE IT.
Got that? Story first. Novel second.
That being said, regardless of any assertions to the contrary, it's not the agent's job to sell whatever you give them. Publishing doesn't work like that. Take a gander at
The Time Traveler's Wife--once again, going back to the recent comments of agents and editors I noticed at the RT convention. In her case, she rushed a "second novel" out, trying to capitalize on the momentum of the first, and it didn't do her career or her publishers any favors. Why? Because she produced a book, not a story.
You have got to focus on the story, not the final product. And you can't approach it from some arrogant "the agent will sell what I send her" angle either. That's no longer the way it works. Your primary goal is to entertain the readers your first book snared. Everything else? It comes further down the line.
So writing a second novel isn't much different from the first one. Think about that first book you wrote. Did you enjoy writing it? Why? What was it about that story that made you want to open your computer every day and work on it? Did you outline? Did you fly by the seat of your pants? What was it about the process that you particularly loved?
Then, sit down and think about the story you've got in your head. Now--what about that story, those characters, the conflict
makes you want to know more? Take a few days and do something else. Take the pressure off yourself. Revisit some old favorites--books, movies, music. Take that day to do something for yourself. Let the idea percolate.
Then come back to your desk with your joy in creation and your excitement in the story restored. Forget about the second novel, forget about the 'problems' and above all, forget about any kind of 'what is my problem?' bullshit and just let the story take over.
It should always be about the story, not the book. Know what I mean? Once your priority is the story, all the rest will fall into place.