20V - Low idle/stall when letting off throttle

[SqueakyP]

I have a Silvertop 20v and am having some issues with idling at the moment. What happens is when I press on the throttle, then let off, the idle goes down to 500 and struggles to stay on, most of the time it will stall. If it stays on for about 5 seconds or so the idle will shoot back up to 900 and stay there until the next time I hit the throttle.

This only happens when it gets to operating temperature, if I unplug the icsv the issue does not occur, but it will have a high idle. The idle will never correct when in diagnostic mode, have to apply light throttle to keep it on.

I have used a multimeter to check the voltages coming from the ecu for +B and RSC, as well as RSO. RSO seems to be for opening, and RSC is for closing. When the motor is near dying RSO is ~2V and RSC is ~9v. When the motor is idling properly at about 900 RPM RSO is 4.6V and RSC is 7.6V

Seems like the ecu is doing this, but maybe there is a chance that my iscv is bad and the voltages that happen when the car is about to die are actually fine for other 20v motors. Perhaps somebody can check the voltage between the pins when idling on their 20v? Pins are below:

http://club4ag.com/faq_and_tech_pages/ECU%20Japan%204age%2020V%20Silver.htm
L1 & N9
L1 & N10


I have also uploaded a video to youtube (http://www.youtube.com/watch?v=PYM8A3S_cUU) showing the problem as well as fuel pressures when it happens, which seems to be fine. I want to note the things I have replaced/checked on this car that may be related.

• TPS replaced and adjusted, IDL switch goes to infinity ohms when throttle is pressed. All other resistances in-spec.
• Knock sensor replaced with one from a 7M-GTE
• Replaced all plug wires, coil wire, distributor cap and rotor
• Checked ECU for leaking caps, there are none and I have tried other ECU's as well. (Both are early model ecu)
• Wiring has been redone; Checked by mr220v
• Have sprayed inside of iscv with carb cleaner, haven't taken it out. I have a video (http://www.youtube.com/watch?v=NI7i4ni79sc) of the max range of movement on the valve itself.
• o2 sensor changed with one from a 4 runner. Plug is the same shape and number of pins, but some protrusions had to be shaved off. Is there some way to check that each pin on the o2 is going to the right place on the harness plug?
• Tried checking for vac leaks with carb cleaner, but couldn't hear any change in engine tone no matter where I sprayed. If anybody has detailed documentation showing each vacuum lines location it would be very useful for me as well as the community.

Any help on this issue would be greatly appreciated. If you need any more information I can provide it.