Micro-Switch Wiring

[Ricker]

I believe that when the engine is cold it idles at a higher RPM than when it is hot. Mine does not. Never has. So I've started replacing and checking different items. I've replaced the Cold Start Valve and now have moved on to the Micro-Switch. It seems fine but here is the question. It appears that a capacitor has been spliced into one of the wires going to the micro-switch. The capacitor is anchored next to the micro-switch with a screw into the top of the inlet manifold. Not sure this is right but the wire is burnt and needs to be replaced. Don't know what size it is or what the part number is. Can't find anything on it. Any ideas?

[sdg3205]

Maybe attach a pic. IIRC, later harnesses have more components to reduce RF interference.

The micro switch is ON/OFF. if you're unsure if it is engaging, you can give the throttle linkage a little help or poke it with a screw driver. If the idle comes down then you need to adjust the stop accordingly.

Also, my idle is always 750 - 800 rpm even when cold running closed loop. The cold start valve is instantaneous and won't/shouldnt be affecting idle.

[Bitsyncmaster]

Don't expect a fast idle during cold weather. Mine never had a fast idle.

That capacitor is just to clean up some switching noise. Some cars have them, others do not. A 1 uf. 50 volt or more capacitor should work if you are changing it.

[Ricker]

38283

Here I thought the RPMs would be higher when cold. I probably don't even have a problem except to replace some burnt looking wires while I have the car down for the winter work.

I know the micro-switch is set properly. I spent a lot of time adjusting the linkage, etc.

I think I attached a picture of the capacitor. It's the one with the yellow wire and attached with the red clamp.

Thanks guys!

[DMCMW Dave]

Check the microswitch with an ohm meter. A common failure is that it will be open when it is supposed to be, but will be 50 ohms or so when closed (should be zero ohms). This causes some oddball idle behavior as the vacuum solenoid will maybe or maybe not close, and the computer doesn't know what to do with that signal.