I am really confused y does car not moving fast i connected the Arduino with 12v adapter
Hi,
Welcome to the forum.
Please read the post at the start of any forum , entitled "How to use this Forum".
OR
http://forum.arduino.cc/index.php/topic,148850.0.html.
Then look down to item #7 about how to post your code.
It will be formatted in a scrolling window that makes it easier to read.
OPs Diagram;
Tom....
You forgot to compensate for the massive losses of that old technology: the L293 drops some 3-4V, leaving a mere 8-9V for your motors.
IF you say you use a 12V adapter why do you post an image (I was hoping for an actual circuit diagram, but no... bleep Fritzing bleep again) with a 9V battery which is totally worthless for a single motor let alone four of them?