做了个图片平滑轮播，但是滚动速度越来越快，求解

<script language="javascript" src="js/jscl.js" defer="defer"></script>
<body>
<div id="top_tg"></div>
    <div id="top_fldhz">
<div id="top_flnr" style="left:0px;">
         <div id="top_flnr1"><img src="web_img/1.jpg" /></div>
            <div id="top_flnr2"><img src="web_img/2.jpg" /></div>
            <div id="top_flnr3"><img src="web_img/3.jpg" /></div>
            <div id="top_flnr4"><img src="web_img/1.jpg" /></div>
        </div>
    </div>
</body>#top_tg{ width:981px; height:600px; margin:0 auto; background-color:#39C;}
#top_fldhz{ width:981px; height:500px; margin:0 auto; background-color:#000; overflow:hidden; position:relative;}
#top_flnr{ width:3942px; height:500px; float:left; position:absolute;}
#top_flnr1{ width:981px; height:500px; float:left; background-color:#FF0;}
#top_flnr2{ width:981px; height:500px; float:left; background-color:#F63;}
#top_flnr3{ width:981px; height:500px; float:left; background-color:#0F0;}
#top_flnr4{ width:981px; height:500px; float:left; background-color:#0F0;}
setInterval(dhTimej,1000);
var i=0;
var dhlbys=1;
var dhTime=0;function dhTimej(){
dhTime++;
if(dhTime===dhlbys*5){
if(dhlbys>3){
dhTime=0;dhlbys=1;i=0;
top_flnr.style.left=i+"px";
return;}else{dhlbys++;
setInterval(liftkz,2);}
}
}
function liftkz(){
var lbjl=dhlbys-1;
if(i>-981*lbjl){

divphgd();
}else{clearInterval(liftkz)}
}function divphgd(){
i=i-3;
top_flnr.style.left=i+"px";

}以上预览的时候发现轮播的速度越来越快
感觉好像是setInterval(liftkz,2)计时器被我反复叠加了，但是却想不出问题在哪0.0！在线求大神指教！