Barometric / Atmospheric / seal level sensor

[Rukus]

My cars barometric sensor has been nonfunctional since i got the car, and i jsut disconnected it. The car seems to run fine. Do i need one for my car to run optimal???

what does it do exactly?

 

[epj3]

Whats up with you disconnecting everything?

You do need it, it measures the air coming into the engine, and compares it to oxygen content in the exhaust (oxygen sensor...) and then the engine computer will adjust the fuel/air mixture to make the engine run properly.

Seriously, stop disconnecting sensors

 

[bichmgnt]

What's a barometric sensor and how did you know it wasn't working?

A barometric snsor would measure air pressue, most likely ambient air pressure. This would let the engine's computer compensate for altitude. But I couldn't find anything about it in the Bentley manual.

Steve

 

[jrt67ss350]

Whats up with you disconnecting everything?

You do need it, it measures the air coming into the engine, and compares it to oxygen content in the exhaust (oxygen sensor...) and then the engine computer will adjust the fuel/air mixture to make the engine run properly.

Seriously, stop disconnecting sensors

That's not quite right - it's purpose is what bichmgnt said. It measures the atmospheric pressure to adjust for altitude variations. When you go higher in altitude, the air pressure decreases and the air thins out. This would lead to a rich burn condition if the amount of gas being injected was the same. Less air + same amount of gas = rich condition. To prevent this, the computer uses a barometric pressure sensor to measure the atmospheric air pressure. At lower pressures, the computer will lean out the fuel to prevent a rich mixture. Theoretically, the computer could just use the O2 sensor to do this, but a barometric pressure sensor is a more direct way of making crude adjustments and then the O2 sensor provides the data for fine tuning.

 

[epj3]

Yes, isnt that what I said? It measures the air coming into the engine.

 

[jrt67ss350]

Eh, guess I read your post wrong. I thought you were saying it measures the oxygen content in the air going into the engine, and the computer compares this to the oxygen content in the exhaust to adjust the mixture.

But you are right - don't disconnect these sensors. If the car isn't running right, then find out why - disconnecting the sensors as a "fix" is not a fix.

 

[epj3]

I do know there are 2 different sensors that we are thinking about and my post wasnt clear, sorry

I cant find a barometric sensor ANYWHERE for any bmw... maybe i'm not looking hard enough.

I also read some places that said the barometric sensor measures pressure in the intake, not the atmosphere?

 

[jrt67ss350]

I do know there are 2 different sensors that we are thinking about and my post wasnt clear, sorry

I cant find a barometric sensor ANYWHERE for any bmw... maybe i'm not looking hard enough.

I also read some places that said the barometric sensor measures pressure in the intake, not the atmosphere?

Yeah, there is one. On my car, it is an oval-shaped plastic thing with "Bosch" stamped on top of it mounted on the engine side of the airbox. I don't know if it would be any different for a 325i. I don't remember where I read that that little thing was the barometric pressure sensor. Anyways, it costs about $200 for a new Bosch one from Advance Auto Parts. Expensive little bugger.

I know that most newer engines (at least GM engines do) measure the barometric pressure as well as an indirect meausre of engine load using a MAP (manifold absolute pressure) sensor, but I'm pretty sure that the M20 doesn't have a MAP sensor. I haven't found one anywhere in the intake.

 

[Rukus]

I know mine doesn't work, because i popped the cover off and it hada piece of paper holding an obviously broke contact away from another contact. i didn't like that, so i unplugged it.

The sensor is exactly waht jrt67ss350 described it to be, its located on the side of the airbox.