At start up it idles consistantly high till warm then it starts to bounce from 1100 - 1300 continously up & down. It does this 100% of the time.

I took off the ISV & cleaned it = nothing.

I unplugged the ISV = same bouncing.

Searching the archives hasn't really helped.

Anyone have any ideas?

Thanks!

Unmetered air leaks?
Clogged Fuel Injectors?
TPS?
-Scott by BOSTON

I soldered mine up but it only lasted a day before they recracked. The new ones have a better design which doesn't lend themselves to cracking.

You could try unplugging the throttle switch and connecting a wire across (I think the bottom two pins) to see if that stabilizes the ISV. Also try cleaning the ISV out with some carb cleaner.

I wrote a lengthy post about this called "wild idle".

I was letting my '89 200QT idle for about 1/2 hour when it started doing the same thing. Aside from test trips around the block, the car hasn't been on the road since I got it for free 20 mos. ago. I rblt the head, had the exh manifold welded (Superior Welding...Pittbrg,PA)and a whole lot of suspension work. The interior gets wet after rains so I let it idle to dry out. Suddenly the idle started swinging from 1000 to 1300. I unplugged the TPS and the revs shot up,unplugged the fuel cutoff and it stabilized but very erratic, unplugged the ISV and nothing changed, ran the throttle bypass screw in and out but little changed, all new seals and gaskets, charged the battery, check alot of stuff. I'll let you know when I fix it.