CIS Temp Switch
 

Here's a pretty esoteric question, but I have faith someone will understand it. On my crankcase breatehr plate at the rear center of the engine there is a threaded hole and a 35-degree temperature switch. I believe this switch tells the CIS system when the engine has reached 35 degrees C, at which time the CIS computer adjusts the mixture (leans it I bet).

My switch is no good and will be replaced. It very probably has been bad for a long time. When I fire up this newly-rebuilt engine with a new temperature switch, is it possible that when the switch turns on, the CIS system will become too lean?

BTW the car started and operated like a dream at any temparature, with the bad temperature switch.

Is that switch seperate from the thermo-time switch that controls the cold start injector? I'm not so familiar with those Computer controlled CIS systems.

I was going to reply along Bill's lines...that this switch prevented gas priming due to temp of engine.

But can I expand a bit? What do you define as "started and operated like a dream at any temparature..."? Did you ever have a momentary stumble, where the idle went quite low then recovered? I have been experiencing this recently and cannot figure out if I need to readjust the CO or what. Temp has been around 30 to 40 degrees.

Anyone with the low-near-dying-then-recover at cold startup? Any fixes for this?

Thanks mightily,
John

John,

Sounds like your WUR might need a little adjustment. The little stumble means it's a little lean at start up.

Don't adjust mixture to fix a cold start problem. Set your mixture for best operation at warm temps, and then fix the cold start by adjusting the WUR.

Thanks Bill - I will take your advice and start by setting the CO at fullup warm.

As to the WUR, that thing scares me a bit since I took it out and could hardly get the square-end machine screws back into the block! But I do remember it seemed clean and the little hole-and-pony show reacted nicely to current. But as for moving that pin, well, I might need some hand-holding here! I will pull out the tech article and have another look.

Thanks again,
John

Thanks for the input guys. I'll check my Bentley. Perhaps this switch is just part of the thermo-time cold start valve thing, in which case neither hot nor cold running mixture will be affected, except at startup.

I know my car does have a separate 90-degree sensor that does impact the mixture control.

No, my SC does not do the almost-die-then-recover bit, but other cars I've had did. I'd guess Bill is right. Partly because Bill has a habit of being correct, and partly from my own experiences.

Hey, Jim!

That switch goes right to the OXS system control unit, so forget about the cold-start enrichment circuit suggestion!