sensor on air box

**esco168** · 06-19-2002, 01:20 PM

does anybody know what the sensor on the air box does? do i need it?

**Anetsberger** · 06-19-2002, 01:31 PM

What year/model are you refering to? I'd be willing to bet you are talking about your mass air sensor. Yes, you do need it. Why would you want to take it off?

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**esco168** · 06-19-2002, 01:44 PM

no not the mass air flow sensor. it has 2 coolant line goin to it

95 m3

**UD///M** · 06-20-2002, 08:37 PM

I think that sensor is a temperature controlled valve. Its only found on 95 and older vehicles (E36 not sure of e30 or earlier). It (I think) controls the flow of hot coolant around the throttle body.

**Des** · 06-21-2002, 07:22 AM

UD///M I have it on my 93 325 and yes you are right about it controlling the coolant as it measures the tempreture of the air coming in from the airbox and open / closes the valve as required depending on the ambient tempreture.

esco168 leave it on. Also when most people fit CAI they tend to not place this sensor in the correct place and so it ends up being left outside the sheilding for the CAI and gets false readings from the hot engine bay, so if you fit a CAI with heatsheilding then make sure that you also place this sensor inside the sheilding as well so that it picks up the air temp and not the engine bay temp.

Hope this helps.

**UD///M** · 06-21-2002, 11:24 AM

Or you could just remove it all and cap off the hoses and not worry about it any more.

**Drifter-X** · 06-29-2002, 08:06 AM

I've recently done this bypass mod. And Wow it not only smoothed out the idle and rev, but gave me 2-5 hp and 3lbs torque. I finally figured out what it was for too. I work at BMW Honolulu and I did some research. I found out that in colder climates most cars have this. What it does is heat the throttle body and prevents the throttle plate from icying over and getting stuck. But it also cancels out the use of a heat shield for a cai. So by bypassing the lines and preventing it from running through the T/B I have affectively reduced intake temps by 10-30 degrees. I recommend this small trick to most people except the ones in colder climates. As odd as a Throttle plate de-icer might sound it is a much needed item in those colder areas. Have fun boys and girls!!!

**Hyperion** · 06-29-2002, 03:34 PM

Originally posted by UD///M
Or you could just remove it all and cap off the hoses and not worry about it any more.

That would be a BAD idea. Temperature effects the performance of the engine. And by allowing too much hot air in (when the computer thinks it is cooler) will make the engine more prone to pinging. So removing it is deffinetly NOT the way to go.

**RRdawho?** · 06-30-2002, 04:50 AM

Originally posted by Des
UD///M I have it on my 93 325 and yes you are right about it controlling the coolant as it measures the tempreture of the air coming in from the airbox and open / closes the valve as required depending on the ambient tempreture.

Hope this helps.

that 2 coolant line thingy that goes into the airbox...thats on my car too...and I have a 92' 325i heeheehee

**pescadito** · 07-02-2002, 04:12 PM

I removed mine. It failed which caused hot coolant to continuously flow throught my throttle body causing pinging. Now I pulled the sensor and connected the hose back into the cooling system bypassing the throttle body completely.

**UD///M** · 07-03-2002, 04:51 PM

Hyperion, apparently you misunderstood what we are talking about. We are talking about REMOVING the coolant hoses from the throttle body. I have been running my car like this since the first week I brought it home. That is well over a year. I have not had any problems whatsoever.

If my 318 had them I would have removed the hoses from it too.

**WJones** · 07-03-2002, 05:02 PM

I took the lazy persons method and left it in the engine bay. It should be closed on warm days, not allow coolant in the TB. In the winter I had no issues.

**nicegsxr** · 07-05-2002, 02:35 AM

Can those of you whose done the removal post a pic or two of the mod please?? I think my sensor is also broken and I wana do the mod since I am in Cali anyways.. it never goes below freezing here. Thanks

**owen** · 07-07-2002, 03:19 AM

Could someone please attach a few pictures, or email them to me. I recently bought a 95 M3, and have noticed a few things that were capped off. I've also found a sensor hanging underneather the T/B...
Please help!

**Hyperion** · 07-07-2002, 03:29 AM

The golden looking thing with the two hoses comming out of the back.

**owen** · 07-07-2002, 04:38 AM

Hyperion - thanks, but that isn't either of the two I am confused about.

Drifter-X - could you please PM, email, or tell us about your T-body mod. I have seen this done on a VW and it helped out a real lot, but I have also spoken to a mechanic that told me it doesn't help much. I'd like to try it myself to find out. Please give me some more info!

**Drifter-X** · 07-08-2002, 08:43 AM

well I did the same thing Hyperion did. I work at the stealership, and the head wrench said that if the temp doesn't fall below freezing. Go ahead and try this mod. You are not hurting anything. It smoothed out my idle, and smoothed out the pulls in the revs. There are three lines. First disconnect the line going from the gold sensor to the throttle body. That leaves one more hose connectted to the throttle body. Disconnect that line and connect it to the open nub on the of the sensor. The line arent too long so be sure to strap it down to a safe place. This is a good DIY. I reccommend it

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**pescadito** · 07-08-2002, 02:15 PM

Okay here's a simple diagram of the sensor and the hoses that I spliced together. Some of you may have done this differently but this is just my interpretation of the procedure.

The RED hoses should be spliced together with a barbed fitting and hoses clamped together. Essentially you want a connection coming out of the engine and back into the cooling system. Or a alternate method is to just cap of the Red holes.

The Yellow objects are things you won't need anymore.

A malfunctioning valve will create very hot air intake temperature causing pre-detonation or pining which was what I was experiencing.

**nicegsxr** · 07-08-2002, 02:43 PM

Thanks for the pics, I just did the mod and boy was I pleased, Plus since my valve was also malfunctioning, I felt a major difference even in 90 degree cali heat yesterday. The idle was much smoother and the power came on much quicker, even when my car is a slushbox!! Thanks!!

**Hyperion** · 07-08-2002, 06:07 PM

But the engine needs a temperature value to associate with the mass flow rate of the engine in order to determine the correct quanitity of fuel needed!

**UD///M** · 07-08-2002, 07:55 PM

Originally posted by Hyperion
But the engine needs a temperature value to associate with the mass flow rate of the engine in order to determine the correct quanitity of fuel needed!

That is done with the intake air temperature sensor. It is separate from the coolant switch thingy.