whats the transistor on the vacuum line bracket on the back of a 1g intake manifold

[bmwisthekey]

there is a vacuum rail on the back side of a 1g( 90) intake manifold, well i noticed that there is some sort of transistor that is bolted to this vacuum bracket with a 2-wire plug on it, it plugs into the same ( male/ or female) plug on the engine wireing harness, does anyone know what this little transistor on the vacuum rail on the backside of the intake manifold is for? thanx, john

 

[DSMcamaro]

weird, I'm pretty sure my 91 doesnt have that.

 

[91eagle_tsi_awd]

i believe its called a noise filter.it sends signal to the rpm gauge.without it the gauge wont work.i need one of those things

 

[bmwisthekey]

we did alot of vacuum line elimination so we took that bracket off, but kept that " noise filter" hooke up and grounded it elsewhere, thanx for the replies

 

[danyz250f]

It might be the knock sensor

 

[compression]

yup, grounded it on on the the throttle cable brackets, ( this was on my gsx ) and it is not the knock sensor, its on its own bolted there, and its 2 wire connector leading to the wire harness, it is only on the 90's because this 92 tsi the engine came out of didnt have that on there.

 

[I_eat_DSM's]

Just to hammer the fact in a little better it is a filter for the tach signal, and it's a 1990 specific part.

 

[FearceDSM]

It might be the knock sensor

Definitely not a knock sensor. Knock sensors are located on the back of the block below the intake manifold.

 

[GORBS88]

Just to hammer the fact in a little better it is a filter for the tach signal, and it's a 1990 specific part.

you got it!!!