D16Y8, manual, P28, HTS basemap. It runs perfect and idles fine, but when I let the gas off and pressing the clutch (no load on the engine), the rpm drops to 0, sometimes the car shuts off and sometimes it recovers itself.
What can I do to fix it through HTS or some mechanical stuff, like adjusting throttle screw or advance ignition with the distributor or something?
Thank you.

 

Unplug the IACV.

Adjust the base idle speed with the idle adjust screw to 450 rpm using an external tachometer.

Reconnect the IACV.

Does the engine now idles to spec?

 

Let me see if I got you. Engine running, unplug the IACV, adjust the screw, and than reconnect the IACV. Doing all this while the engine is running, right?

 

You must disconnect the IACV to set low base idle speed. When done, you can either turn engine off and then reconnect the IACV or leave engine running while you reconnect it. Shouldn't really matter.

Setting the base idle speed is a bit tricky because the engine will want to die at 450 rpm. If necessary, carefully press the throttle pedal to keep the engine from stalling during the procedure.

Use an external tachometer because the cluster tachometer is inaccurate at low rpms.