My engine on the Accord EX 92 act weird after running "hot", the RPM just keep moving up and down between 1000rpm to 1500rpm whenever I break at trafic light, but if I release the break then it's OK. This only happend after running the car for over 20 minutes, before that, engine cool I guess? nothing like mention happend. Would it be the Idle control sensor or someone mention to me it's the break master cylinder. Any suggestion please? Thank you

 

Search for 'idle surge' or 'IACV'.

But if it ONLY happens when your pressing on the brake pedal, then it sounds like the brake booster is leaking vacuum. Check this every which way, brake on/off to prove it's caused by the brakes.