[Supras] Help! Idle cutoff cycle

[berniek at technicaldevelop.com]

Dear list:

    Just got my '91 turbo from Texas 15 minutes ago.  Seems fine except 
that idle cycles from about 800 RPM to 1500 every second or so.  I need 
to leave for work now, but get it inspected tomorrow.  So any hints 
would be appreciated.

    I loosened the top screw for idle throttle switch to try rotating 
it, but there apparently is a screw on the bottom as well.  I did not 
have time to get to it.  I disconnected the ISC connector and nothing 
changed, so the fuel is cutting off when the engine speeds up to 1500 
RPM, and then turns on again at about 800.  So I suspect the throttle 
switch but will need to examine it further later.  If its any help, the 
former owner installed a Greddy turbo timer, which gave the correct time 
delay (about a minute) but I later turned it off and the engine stopped 
when the key was turned off. 

    So I'd appreciate hearing from anyone about the cyclic idle 
problem.  I'll try to get to the bottom screw for the throttle switch 
after work, but it looks as if someone has tried that before.  Any hints 
would be appreciated.  I did not have time to pull codes, but the check 
engine light is off.

    Thanks.

       BernieK