Low Idle When Using Brakes

[2fotee]

96 240SX, AT, 160k miles: After my car's engine warms up, when I apply the brakes and come to a stop the revs dip to 400-500rpm. The car doesn't stall but it's just 'too' quiet. The problem just started a month ago and has become a little worse since then. The ECM is giving codes 0304=knock sensor, which I haven't been able to get rid of by replacing the sensor or the sub harness, and 0707 the rear oxygen sensor. What things should I check for?

[vancouverbc]

http://www.obd-codes.com/troub...n.php

the fsm tells you how to check out the knock sensor circuit when you get the code

[navysnail]

this only happens when you hit the brakes right and not when its just idling? if so, check for a vacuum leak around your brake booster and the vacuum hose that supplies it, it can crack around the bends and near the intake manifold.

[remzon]

Hey 2fotee. I have a 93 240sx with KA24DE, exact same problem. RPMs drop when i apply brakes and come to a halt. I haven't checked my booster line yet, like the other guy suggested but i'm going to soon. Did you ever find out what was causing your problem??