throttle position switch (TPS) .vs. idle speed switch (ISS). my 951 hunts for an idle when hot, usually wanders from 1000-1500rpm. I've read in past forum posts its usually one, or both, the TPS and ISS. I've tried to listen for the "click" of the TPS just off idle. no noise at all. (how loud should it be? I've used a hose to my ear and still hear nothing). the plan is to liquid-wrench the screws and try to adjust the position, listening for this click. if after moving the position from max to min and I still don't hear anything, I got to assume the
sucker's dead! and that's why the idle hunts because the "brain" still thinks it's open and therefore still calling for more gas than enough to sustain an idle....
but, if I hear the click, adjust the position and it still does it I should zero in on the ISS?

 

Yeah, undo the screw and twist the TPS until you hear the click. It's definitely audible in a garage with background noise. If you have sensitive hands, you can even feel it.

Most likely your hunting idle is a vacuum leak though. Probably in the rat's nest of hoses under the intake manifold.

 

I don't know if mine is busted or not, but when mine "clicks", its too quiet to hear when the car is running. I can only hear the click when I move the throttle body by hand when the car is off.

 

well I heard the click, so I guess its NOT the TPS. I'll move on to the ISS to solve my idle situation. interestingly, when the idle is high, just tapping the ISS with a screw driver has a reaction to the idle... guess I'm answering my own question...

 

Yup you did just answer your own question

Sounds like the idle stabilizer is sticking...carb cleaner works well

 

How big of a job is it to pull the intake manifold off to get to the idle stabilizer?

 

just did the Gum-Out spray into the big vacuum hose from the manifold into the ISS and then can-of-air to dry/evaporate/flushout any junk that may have been there and it's better. so far, when its hot it only come up to 1200 rpm.
maybe a few cycles of this cleaning could avoid the intake removal.
thanks for the tips...


'88 951 stage II chips, cone intake, cat by-pass, yellow konis, 250# springs