A few idle issues.

[JMiller]

Ok my car has been surging bad for a while. I swapped out ISCs and removed and cleaned the entire Throttle body. I also have the BISS screwed all the way in. Now when i push the gas it will rev up then drop to 1000rpm then sit there. But when its sitting at 1000rpm if i push the gas a let off real quick it will drop to 400-600rpm and sit there until i start moving again. Im ordering a complete block off plate for the FIAV and ISC and getting a new o ring for my BISS. But why does my idle settle down when i slam the throttle plate shut? I know i have enough slack in the line. Any help would be great, thanks.

 

[bboyalan]

What exactly are your cold and warm idle rpms at? Have you ohm-tested your ISC yet?

 

[JMiller]

cold idle 750 warm 400-500. I bought a new ISC and still same thing

 

[rush2252]

sometimes people confused a bad ISC with a boost/vacuum leak. If you have a bad BISS oring or TB gasket or even intake gasket it will cause goofy idle surge because the ISC cant adjust enough to maintain idle. Try checking the intake mani and TB gaskets as well as clean the TB. Make sure the TB shaft seals arent shot you shouldnt have much play in the butterfly valve. If you have even the smallest boost leak post TB it will cause idle surge.

 

[JMiller]

I did a BLT on the throttle body back and the only thing leaking was the BISS. I'm going to get a new o ring for it today.
(update)
I got a new o ring for my biss and with it screwed all the way in, it will either idle at 1000 or under. I've actually got it to sit at 300 for a while.