Seeing sens-or

Being a typical techy with a new toy, I’ve been reading the M3 forums and I came across this one where a lot of people are reporting a noticeable improvement in throttle response and idle after cleaning the MAF. (Mass Airflow Sensor)

And seeing as I’m intending to get a bit more hands on with this car, I thought I’d give it a go.

Of course I had to pay the notorious ‘M tax’ on the tools as it needed a security torx spanner… £13 a set. (I know that doesn’t sound much, but they’re just glorified allen keys!)

After the nicely engineered German clip was unclipped and the two torx bots were undone I removed the sensor and set about it with good old Halfords electrical contact cleaner.

The hole in the middle of the picture is where the sensor came out..


And here’s the sensor itself..


It was pretty manky so I gave it a second dose and waited for it to dry.

Once dry, I put it back in and crossed everything whilst starting the engine. Hurrah, it started and idles ok so I didn’t make anything worse! I took it for a quick spin and whilst it might have felt a little more responsive it wasn’t that noticeable, if at all and there’s still a little hesitancy when cold.

But it still goes like an absolute rocket and makes everyone else seem like they’re driving at walking pace, so perhaps it’s a good thing that it’s not any faster than it was!

After looking into it a bit more it seems that the people who notice the biggest improvement have changed their OEM air filter for either a K&N or Streamlined Engineering (SE) filter. Where the standard filter is the usual paper/mesh based affair, the K&N and SE filters are what’s known as ‘oiled’, which means the paper is soaked in oil to improve the filtering capability.

One down side of these filters is that the oil can come off them over time and coat the MAF sensor, and as the sensor is self-cleaning (by heating up to 600 degrees to burn the crud off) it’s never changed as part of a service.

As mine has the standard air filter, my sensor was still clean enough to be working as advertised.

And who said you can’t learn stuff from the internet!