Blacktop 20V high idle

[Bravothreezero]

Anyone have experience with this?

My blacktop idles at 2000 rpm. Only there is a catch. Sometimes it will calm down to 1000. But when I rev it up it will stick again at 2000.

My first step will be cleaning the ISAV (i.e. ISCV). A sticky bi-metallic spring could cause a high idle. It pushes open the valve to the bypass air intake.

However... it does not make sense to me because once the engine is hot, that bi-metallic spring is not moving anymore right? It would be fully expanded. And if it's not moving, how can I have 2000 rpm but sometimes 1000?

I also read that there are two solenoids in there, connected to the ECU. As I understand it they make sure the rpm is stable under various loading conditions (also by controlling the valve to open the bypass air intake).

Can the ECU also "command" a 2000 rpm? That it somehow thinks the engine is still cold?

[decryphe]

I'll be monitoring this thread, my 16V bluetop with OEM ECU does the same.

A quick tap on the gas pedal generally unsticks the system and idle drops from ~1800 to ~1100 rpm. Does yours do that too?

[ondafly]

Mine will idle at 2k when cold and after roughly 5minutes it will drop below 1k. If aircon is on, it will sit at 1k after its warmed up. I've always felt the idle was a smidge high, but I'm not sure what is normal to begin with !

[jdm86gtz]

The ISCV is fully electric and controlled by the ecu on the 20v.
When it's idling at 2000 at normal operating temperature plug the inlet pipe to the ISCV and see if that drops the idle back to about 850rpm. If it does then the valve is probably gummed up and could do with being cleaned out with carb cleaner etc.
If it doesn't you will have to look for other vacuum leaks.
Also check the vacuum actuator under the throttle bodies that catches the throttle linkage and slows down the final closing phase when you release the pedal.
Also if you can see the throttle blades make sure all 4 are closing together as they are split 2 +2 by the linkage setup.