88 5KTQ this week my idle speed has gone up

[Cody Forbes]

JeffreyZentner at aol.com wrote:
> Hi All
> I have an 88 5KTQ this week my idle speed has gone up. Normally and
> now when I first start the engine it idles at between 900 and 1200
> rpm. Now after the engine has warmed up it idles at about 2200 and
> then goes down to about 1800 rpm. I have checked the throttle and
> cruse control cables and they are not holding up the idle. What will
> cause this?
>

The idle switch on the passenger side of the throttle body is a very likely 
culprit. First try listening very carefully while slowly opening and closing 
the throttle with the engine off (from in the engine bay). The switch should 
click just before the throttle is fully closed and just as it starts to 
open.

If it doesn't click you can try adjusting it, there are two small (6mm head 
IIRC) screws, just loosen them and rotate the switch a little and listen for 
the click. Still no click replace switch.

If it does click initially it may have a bad contact at the plug, or could 
just be bad. Check the plug for corrosion, and many times just disturbing it 
by unplugging and plugging back in will help intermittent connections.

Another test for the idle switch is to unplug the connector and use a 
paperclip or something to connect the middle pin to whichever other pin has 
two white wires comming off of it (my Bentley manual is not handy at the 
minute). It's a 3 pin connector, the center pin is common, one of the others 
has two white wires and the remaining outboard pin has only 1 wire (that's 
the WOT switch wire). With those two pins jumpered together check your idle 
speed, if it's still high then it's likely not the idle switch. BTW, if the 
check engine light comes on when you jumper the pins together then you are 
on the wrong two pins.

-Cody Forbes
http://www.5000tq.com
'87 5ktq - Fast.
'87 5ktq QLCC'd plus some
'86 5ktqCD
'86 5k
'86 5k