Rebuilding a BMW intake: S52 to M50 manifold conversion, day 6

Coming to you live from my parents garage in this 7 part series, are the chronicled adventures my dad and myself had converting an S52 intake manifold to the larger M50 intake manifold. Day 1    Day 2    Day 3    Day 4    Day 5    Day 6    List of parts    Day 7

With my car still running terribly (misfiring like crazy), I head down to Gary’s shop to see if he had any ideas.

Talking with him, he was pretty adamant about saying he no longer performs M50 conversions on S52 motors–a majority of the time they don’t work (like mine) and because they are such a pain (as I now know).

His first idea was the mass air flow sensor was bad–this was interesting, because this was my original thought many weeks ago before I decided to do the conversion in hopes of fixing a vacuum leak under the manifold (apparently replacing the manifold didn’t help, doh!).

So he brought out the diagnostics and we went over and had a look. We turned the car on and unplugged the MAF–that shouldhave killed the engine because it would have detected no air entering, but instead the car still ran. Hmm… that was odd.

Then, we revved the engine a number of times and noticed something interesting–the MAF was reporting a drop in air levels, with full throttle!

So that seems to be the new problem (and not a cheap one, $300 for that tiny little sensor, doh indeed).

But now the question is, has this been bad all along and been contributing to my rough running engine (which is now even rougher).

Talking with a new mechanic at Gary’s shop (former Porsche mechanic), he said yes this is likely. He explained that cold air intakes with their “reusable” filters are in fact, not reusable. Using oil to clean this filters actually destroys them, opening up the pores and allowing particles 5x larger than normal to enter!

This was confirmed by a filtration expert who worked at nuclear power plant and measured filters before and after oiling/cleaning.

Turns out K&N knows this, but are obviously not going to pull these expensive filters off the market for obvious monetary reasons.

So thinking way back when, right around the time the car was running rough I believe I oiled and cleaned my filter, doh! This likely led to the destruction of my MAF over time, which would explain why nothing I did fixed the problem :-)

Guess I need a new filter to go with my $300 MAF, lest I break it again :-)

I called up Bimmer Performance Store to order a new aFe filter and guess what! The rep I spoke with told me that aFe has just released (like 2 weeks ago) a brand new air filter that does notneed oiling/cleaning. It will last up to 30k miles or longer depending on the climate and simply needs to be vacuumed that is it.

The rep went on to further explain that this was in response to loads of MAFs going bad as a result of oiled intake filters.

So ahah!

Could this has been my problem all along?

Regardless, taking the intake off and replacing all of those hoses and reseating everything was certainly a great preventable maintenance.

Will this work? Let’s hope so, stay tuned!