On my 2000 Legacy Outback wagon there is a valve ? of sorts that feeds mixture in after the throttle plate. I had it apart to clean when cleaning the throttlr body. Further down stream is another electrical connect to some sensor bolted in the plenum.

3 qUestions

What are they called? What do the do? Do either have any interaction with the transmission in any way?

TIA Jim

On my 2000 Legacy Outback wagon there is a valve ? of sorts that feeds mixture in after the throttle plate. I had it apart to clean when cleaning the throttlr body.

IAC

Idle Air controller. It is what regulates the air into the engine at idle to keep it running. It is also what allows more air in for high idle like when the AC is on.

 

 

Further down stream is another electrical connect to some sensor bolted in the plenum.

MAP

Manifold Absolute Pressure. This is a secondary way along with a MAF Sensor(Mass Air Flow) of measuring how much air is being pulled into the engine.

 

Do either have any interaction with the transmission in any way?

TIA Jim

 

Nope. They only effect how the engine is running. The amounts of Fuel it gives, and the amount of spark timing advance.

 

The only thing that would effect the transmission is the TPS or Throttle Position Sensor. This sits along the axis of the throttle plate, on the opposite side from where the throttle cable attaches. It will tell the TCU (Transmission Control Unit) what position the throttle is at, and based on it's reading and the RPM of the engine (and a few other things) it will decide if it needs to down shift, up shift, or stay where it's at.

 

Keith

Thanks for the explanation of the first 2.. I am familiar with TPS having one in an older Bosch system.If the TPS was reading a higher than actual idle would the ECU or what ever cause the transmission to try to engage . The problem I actually have is the transmission engaging with the idle down around 600 or so. I get a shuttering when I hold my foot on the pedal. When I release it the car moves slowly ahead. When I move it to neutral there is no change in RPM. Any thoughts

Exactly what problems are you having?

 

 

nipper