throttle valve switch - what exactly does it do?

The throttle resting bolt on my car had been adjusted so the car was, including on idle, permanently ticking over past the point where the throttle valve switch clicks (open or closed, not sure).

I'd like to learn exactly what the switch operates. It must send a signal somewhere but what is it telling what to do?

This could be the answer to all my cold start problems, after having chased them around the car.

Much appreciated.

I plan to post a looooong thread on this once solved as this has kicked my ass, a bit.

if k-jet, the switch on the throttle body is for the cold throttle enrichment system, it sends 12v when the throttle is open to the vac switch. Its the round metal valve with a vac pipe and 2 pin plug behind the airbox.

The valve closes when it detects a hard throttle condition, which in turn passes 12v to the 5th injector. since 5th injector is earthed by the thermoswitch, this only happens when engine is cold.

By open throttle, you mean no throttle, yeah? So when in the idling position, it sends to the vacuum switch / diaphragm and then when it moves past the click, it changes to give 12 volts to the cold start injector, but only when the engine is cold? Have I got this right?
So while mine, previously, was idling permanently passed that click position, there would never have been any signal going to the vacuum diaphragm thing, which would have meant the idling mixture was wrong.

I tried it again last night, when cold, to see if having corrected the position of the throttle improved it all, but it was hellish lumpy again and stalled if not given any throttle. I'm sure all these steps will lead somewhere eventually though. Cheers for that.

no I do mean open throttle
Wouldn't be much use having a throttle enrichment system that only works if the throttle is shut eh

when the switch is clicked shut no voltage is sent, i.e. throttle closed. when the throttle is off idle the switch sends 12v. The cold throttle enrichment valve is itself a switch, which passes current when a hard throttle condition is detected via the vacuum hose.  It only works when cold becuase the 5th injector earths via the thermoswitch, the earth path is lost when the engine warms.

The idle switch shouldn't have effected the idle at all, unless the cold throttle valve was faulty and stuck open, therefore holding the 5th injector on.

1st check is for 12v at the idle switch plug, then check at the vac switch for 12v at the wire from the throttle switch when the throttle is open. Next with the engine fully cold, check for continuity to ground at the green/white wire at the 5th injector.  Finally, check this again when the engine is warm

to check the vac switch works you check for continuity across the 2 pins if you rev the engine hard.

yeah, as you may have guessed, I'm quite a newbie at all this malarky!

still lost as to the cause of a cold lumpy start up. it runs fine once warm. looking forward to the day when i can post all this with som sort of happy ending!

cheers for the information.

start with the basics, air leaks, timing setup, co adjutment etc. if it still does it then it could be a problem with the k-jet system, trouble is with this if you dont start with fuel pressure checks you can be chasing a problem round for ages swappign things till you stumble upon the problem

it does sound like it may be the WUR at fault, but without fuel poressure checks its a bit of a guess!

checked fuel pressure, hot and cold. changed thermotime switch, tested cold start valve and injector. checked main injectors. removed and cleaned up metering head. tested for air leaks. checked wur.

got a friend coming over on the weekend with an identical car to take a look.

fingers crossed.