Okay i was quite confuse about this !! I have a big Portal related to
online sale purchase of old and new cars !!
Now it have nearly 1Million Listings of old and new cars !
I had tried my best to put them in proper categories !!
Now i have a inhouse tool with the help of which i can approve and
disapprove popular search keywords !!
Well its like .. some one searched for "Accord 3.0" now if i find its
a good keyword .. then i can approve it !! Now once i approve, it will
generate a new automatic webpage with something like:
http://mywebsitename.com/blah-blah/blah/accord-3.0.html
and the page will be containing listings of all the available Accords
on my website with 3.0 LTR engine !! This page will contain listings
for OLD Accord + New Accord ! having 3.0 ltr engine !!

My question is will search engine recognize this as Dupe-content or
Doorway pages ?

I'm worried after i had seen in update of Doorway Pages definition:
"Doorway pages are typically large sets of poor-quality pages where
each page is optimized for a specific keyword or phrase. In many
cases, doorway pages are written to rank for a particular phrase and
then funnel users to a single destination."

Please Note: I have Something around 11,700 Popular Search Pages !!
With niche Title, Description and Keyword Tags !!

Please advice !!

I think you may have misunderstood a Doorway Page...
"... Doorway pages are typically large sets of poor-quality pages
where
each page is optimized for a specific keyword or phrase. In many
cases, doorway pages are written to rank for a particular phrase and
then funnel users to a single destination. ..."

The key parts here are...
"... poor-quality pages ..."
and
"... then funnel users to a single destination ..."

Are the pages your site is creating meant to hook in readers, then
send them of to the main site?
Are they heavily optimised pages with links to less relevant content,
and merely there to get visitors?

.

Doesn't sound like it to me.
Sounds like you have a way of creting pages that meet search demands,
and show topical/relevant information.

.

That said, I can see a possible duplication issue... as it means that
some pages are likely to have very similar/same content (that happens
when handling data quite often, as the same info can have many
relations).
So it may be worth looking through and making sure that you are not
generating pages with basically the same content but different URLs.