Can't find the intake air sensor 95 M3.

[scotts364]

I have had problems with eating up catalytic converters in my 95 M3.
I replaced most of the engine management related sensors, spark plugs, but eventually had to replace the cats. The following year I failed just as bad high HC and NOX.
I bought a new intake air temp sensor the first time but could not find where it is located in the vehicle.
Bentley shows it in the intake plenum close to the throttle position sensor.
I found a note somewhere that it may be located in the air box but the only item/sensor in the air box has 2 rubber hoses coming off of it.
The only other temp sensor I can find is in the air left side brake air duct which has a yellow body and no threads.

Any ideas?

[Jeron]

Its on page 610-5 in Bentley. On the S50US the intake temp sensor is in the intake manifold behind (firewall side) the throttle body.

[scotts364]

Thanks for the reply, but as described in my original post, the sensor IS NOT where shown in the Bentley manual.

As a matter of fact, I have looked from where air enters the grill to the cylinder head without removing any parts and I cannot find it anywhere.

Any chance that is uses the same sensor as the on board computer?

Scott

[Jeron]

Realoem appears to show it in the same place as the Bentley.

On the S52 manifold it is on the bottom of the manifold just (an inch or 2) past the throttle body.

On yours what is in the hole in the manifold that is behind the throttle body.

[scotts364]

There is no hole in the manifold. There is a possibility that it is under the manifold but hidden by the hoses on the bottom of the throttle body, I will take a look when I get a chance.

I have new cats and O2 sensor on the way and I noticed I got a knock sensor #1 code so that may help explain the high HC and NOx. I want to check all the components before I put on any of the new parts. I went through this a few years ago and replaced plugs and O2 sensor and it passed (barely). The next year ended up having to replace the cats to get the NOx to pass.

The NOx now are about 2100 and should be around 900. HC's fail but only by a small amount over the standard. Car runs great especially now that I replaced the lifters, good throttle response, good power.

I am going to measure the connector points at the DME today. With the connector unplugged it should measure the same as the sensor.

Scott

[scotts364]

FYI
I found a picture of the bottom of an M50 manifold that had the sensor under on the bottom of the manifold about even with or a little closer to the firewall. I just checked and sure enough that is the manifold I have.
Thanks
Scott