Microswitch test for idle issue
 

Good morning, thanks for the help with the ICV test.

Related to that I am trying to diagnose an idle issue (won't consistently) and I pulled the plug to the idle microswitch.

I am not hearing a good "click" when I move and then return the throttle to the closed position, and I am not getting any chance in resistance when I open the throttle and have leads on both of the two prongs. The car is not running when I did that test, but that shouldn't be necessary to test the switch, right? I am basically getting a closed result on the OHM meter of infinite resistance.

My conclusion is that I have a bad microswitch, yes?

infinite is open.
the meter may show OL for this.
a short or closed contacts should have a "." like 00.40 or 0.60 or 1.2.

see if the switch is adjustable. it may rotate.
there may be a small throttle stop adjuster on the TB. this should not be messed with. if someone did use this to "raise" the idle that would explain why the switch is not working.

Thanks for the response, sorry if I goofed but the Ohm meter reads "1" meaning I don't have continuity.

I assume you are working on your 74, correct? I am not aware of a micro switch that affects the idle. The only micro switch of which I am aware is the one on the throttle body that engages the cold start valve when the engine is cold. If that is the switch that you are testing, it very well may be bad, but it would only prevent the cold start valve from opening during a cold start. It does not do anything once the engine is running and does not influence the idle.

If you are speaking of some other micro switch, I apologize for deflecting the thread.

Hi L.J. - sorry for not being more explicit, this is the one with the 3.2 in it that has a microswitch near the ICV that helps manage the idle.

There's an adjustment screw on the left of the TB just for this.
I'll look for a pic.

Wah-lah

http://forums.pelicanparts.com/uploa...1491244934.jpg

Per Dan's diagrams, I'd check to make sure the throttle arm is making contact with the switch. I chased an idle problem that ended up being vacuum related. If cold and you're getting almost a cam lope idle I think I'd start by verifying your vacuum lines are good. I had a few that needed replaced. I then installed a wideband in my car and made sure my base idle was set. I'd drop Sal (Scarceller) a PM and see if he'd be kind enough to walk you through the proper setup for the car. I'd post his procedure here but I don't want to step on any toes. Sal has a very thorough step by step process that makes sure everything is right.
In my case the idle would improve once the car warmed up but it would still search at a stop light. The vacuum lines made a big difference but so did getting my idle air and and base idle set.

+1 and I'd recommend keeping your efforts all in one thread.

Thanks gentlemen, will get under the car tomorrow. Very much appreciate the help.

On the back of your air filter box there are I think 3 hoses that come off of it. One goes to the breather line on the oil fill neck. I think another goes to the back of the throttle body and has a formed bend in it. Use a flashlight and mirror to visually inspect them for any bigger cracks. My line on that went to the oil fill tube had a bad crack in it. I think there was one leaking on the back side of the throttle body as well as one leaking at the Cruise control actuator. On the throttle body, roll the throttle back and you'll see the idle switch. You could take a screwdriver and actuate the switch while checking continuity. When it closes your meter should read 0.00 and open 1 based on your description of the meter. There really shouldn't be a resistance reading when the switch is isolated since it's simply a switch, open or shut.

Pulled the switch today and look what I found;

http://i207.photobucket.com/albums/b...pslae3xson.jpg

That explains why it wasn't working I suppose. Grin.

One tip to pass along is that you should check that it is working before buttoning everything up since there is a range of installation angles as indicated above, it is possible to install it and it not make contact thereby defeating the purpose. Check that the resistance changes from 0 - 1 with an OHM meter.

Thanks for all of the help folks - much appreciated.

You are the man!
sorry for the surprise, and thanks for the feedback - Good luck
(file under: Yup, that'll do it department)

It actually idles now - such a luxury!