idle problem.. wat is a BISS?

[dieschachtel]

hi, my idle is steady when cranked cold at about 2000 rpm
's. once car warms up the idle surges from 1500 to around 800rpm's. when the car is in drive(auto), the rpms hold steady at about 750+- and it does'nt surge. I heard about a BISS screw and i dont know what it is .. Could someone help me out here?

 

[mitsuclipsegsx]

hi, my idle is steady when cranked cold at about 2000 rpm
's. once car warms up the idle surges from 1500 to around 800rpm's. when the car is in drive(auto), the rpms hold steady at about 750+- and it does'nt surge. I heard about a BISS screw and i dont know what it is .. Could someone help me out here?

my car was idling like shit , i found out it was the bliss screw,it was almost all the way out,i just tighten it all the way and back out 180 degrees look at vfaq.com too

 

[blcknspo0ln]

search VFAQ and our tech articles for "idle surge"...

also, the BISS is the base idle set screw located next to your 3 vac nipples on your throttle body, its adjusted by the phillips head.

My suggestion would be to check your ISC (Idle speed control) motor. check the coils on it via multimeter and make sure its still OK. then go ahead and adjust your TPS (throttle position sensor) to spec. These are all found on your throttle body.

if you do'nt know where your throttle body is, you have a lot of research to do

 

[dr_fatkins]

The BISS (Base Idle Set Screw) is a passive bleed point on the throttle body. It is circled in purple in this picture. To decrease idle, turn clockwise being careful not to forcefully bottom it out.

 

[dieschachtel]

my car was idling like shit , i found out it was the bliss screw,it was almost all the way out,i just tighten it all the way and back out 180 degrees look at vfaq.com too

Heh Heh. I purchased the car with a hole in the intake, i managed to figure that a screw of some sort should be there. am i gonna need to hit up a junk yard for it or should i order a new one?

 

[xveganxcowboyx]

The BISS should not cause your idle to surge. It simply controls the idle speed. Of course if it or something else is leaking boost/vacuum then you might have an idle surge issue. So on top of checking you TPS (throttle position sensor) and ISC (idle speed controller) you shoud check for boost leaks. They commonly occur at intercooler couplings, BISS seal, Throttlebody shaft seals and injector seals. I have replaced all recently on my car and none of it was particularly difficult.

 

[xveganxcowboyx]

Heh Heh. I purchased the car with a hole in the intake, i managed to figure that a screw of some sort should be there. am i gonna need to hit up a junk yard for it or should i order a new one?

Where is this screw missing from? Could you take a picture? If it's the BISS you can order a new one easily (about $10)

 

[dieschachtel]

Where is this screw missing from? Could you take a picture? If it's the BISS you can order a new one easily (about $10)

Yea, the screw was missing when i bought the car i just never could figure out exactly wat went back there. i checked the chilton and hayne manuals but never could get a name for the missing thing.

 

[xveganxcowboyx]

http://www.slowboyracing.com/more.php?id=3753&PHPSESSID=8e34d806cc50d9afa30fa6f32a15009b

 

[1glaserturbo]

The BISS should not cause your idle to surge. It simply controls the idle speed. Of course if it or something else is leaking boost/vacuum then you might have an idle surge issue. So on top of checking you TPS (throttle position sensor) and ISC (idle speed controller) you shoud check for boost leaks. They commonly occur at intercooler couplings, BISS seal, Throttlebody shaft seals and injector seals. I have replaced all recently on my car and none of it was particularly difficult.

My idle surged before I set my BISS down a few turns or so, now it idles perfectly at 750 rpms. That seems to be your problem, if the BISS is missing, get a new one and screw it all the way in, then 180 back out. You should be fine then.




Chris

 

[xveganxcowboyx]

The BISS also has an o-ring sealing it from the atmosphere. An open BISS hole would constitute a substantial boost leak. He can expect a gain in power and smoothness on top of a stable idle.