what does the "sensor "on the side of the TB do
 

Hi got what looks like a sensor on the side of the TB . what does this do?Thanks

Sounds like a Throttle Position Sensor to me. Do you have a picture to be sure? It basically tels the ECU what the position of the throttle is (hence the name:-).

here it ishttp://forums.pelicanparts.com/uploa...1253069407.jpg

That is a TPS fo sure.

Why is there a TPS on CIS?

that was my next question?

It tells the lambda ecu or k-jetronic box under the driver seat the position of the throttle butterfly and sets the base duty cycle of the frequency valve relative to the position of the throttle butterfly after the temperature sensor in the passenger side timing cover decides the engine has warmed up enough.

The oxygen sensor's output then tells the ecu the O2 level in the exhaust and the the ecu adjusts the frequency valve up or down to fine tune AFR for lower exhaust emissions.

What year-model is the car? If I have time I will look it up on the PET.

JFairman, excellent explanation.

Bill

You can see the fitting and fuel line going to the frequency valve on the silver USA fuel head in the picture he included so that is what the throttle position switch is doing on this car.

It's the small one to the right of the large rubber fuel inlet on far left of the fuel head and that doesn't exist on a ROW or euro fuel head from '86 and earlier so this appears to be an '86 through '89 USA motor in this picture.

You also see the where the frequency valve return line piggybacks onto the return line banjo bolt along with the WUR return line on the right side of the fuel head.

At or near full throttle the TP switch tells the ecu to ignore the O2 sensor output and it goes into open loop mode and the frequency valve stays at something like 70% duty cycle or something like that to richen up the fuel mixture when the turbo is making boost.

The way it does this is another story... It's all here if you can find it with a search.