why do i Have two O2 sensors before the Catlytic converter?

[darsh4126]

Yes there is a little cat look like that hanging from the manifold, but i never thought that is cat. The cat that i knew was the one underneath in the middle. THat make sense too, because when i look at the second O2 sensor values it shows very little variation above 0.45Volts(unless when lean). So, it act's like there is a cat before that.

Hey did you look at my Engine misfire post? do you have any thoughts on that?

thanks

[MMamdouh]

IMHO,
First O² sensor try to control air/fuel mixture feeding engine.
The second O² sensor is there to control if first cat (pre-cat) is doing its job correctly.

+1

MMamdouh

[MMamdouh]

Intersting. Where are you located?

cairo, Egypt

Can you post a pic of those two sensors?

first sensor:


second sensor:


and here you can see the first cat attached to the exhaust mani:


MMamdouh

[benzino]

is that inlet manifold with the quad throttles from a daewoo?

[Fltofancy]

That is the intake manifold, partially disasembled, from a 1.6L Daewoo engine. The butterfly valves are part of the variable intake runner design. They are vacuum operated and open or close to change the intake manifold runner length, thereby tuning the intake manifold to the engine rpm. This tuning of the runner length gives a slight positive pressure wave just as the intake valve is closing and "stuffs" a bit of extra air into the cylinder. Notice all the black carbon buildup....thanks EPA for the EGR valve!

Fltofancy

[benzino]

i knew the 1.6 had variable intake runner length but i thought it was just a flap rather than actual butterfly valves...

[darsh4126]

This is the exactly how it looks like on my car. thanks for the pictures MMamdouh. By the way did you look at my Daewoo TIDs and CIDs post? I really need help here.

Manufacturer defined TID $02, component ID $50 fail.

Thanks