Fixing fast idle on 5kcstq

[Tony Lum]

Hi gang,

Been fighting intermittent high idle (1000-1500 rpm) on my '87 5kcstq 
(MC-1).  Went after the usual suspect, the idle/wot switch.  I had no 
contact with the throttle at rest, but when I pulled the switch it tested 
good.  Reinstalled it and realized that sometimes I couldn't hear the idle 
microswitch click when the throttle valve hit the rest stop.  The switch 
adjustment was at its limits, so I whipped out my Dremel tool and elongated 
the slots to make sure that switch was closed at idle.  That eliminated the 
really fast idle, but I still had a intermittent idle that ranged from 
800-1000 rpm.

This got aggravating in rush hour traffic as well as wasting some gas, so 
when I got home last night I unplugged the ISV and restarted the car and 
the idle was unchanged.  Checked the hoses and they seemed ok.  Then I 
checked the idle screw in throttle body.  Bingo!  The idle screw was very 
loose.  Screwed it down, plugged in the ISV, restarted and idle was back 
down to 750 and stable. Yes!

So don't forget that idle screw when diagnosing a fast idle problem.  With 
a working ISV, the idle air screw isn't needed and should be tightened till 
seated.  Its probably a good idea to check the o ring on the screw as well.

Regards,

Tony
'83 urq #302
'87 5kcstq


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