Following my post last week on the BMW, I figured I needed to take the ECU out and take a look at the solder joints to see if there was a loose connection somewhere.

Getting the ECU out of the glove box is pretty easy, but that’s where it stops being easy. These ECUs have metal tabs connecting the top and the bottom, in addition to some nylon connectors holding the boards in place. The metal tabs are bit of pain especially since there are a bunch of them.

Once I got those those I was able to take apart the two halves but this ECU is old enough of it has two boards sandwiched together. They are held to the bottom half of the ECU with a few screws and nylon pins that only the Germans could engineer. You can’t tell at all how to get them apart. You pull up on the pin and the collar stays in place that loosens as the pain gets narrower towards the bottom.

I finally got the boards apart, inspected them and added a tiny amount of solder to the three joints that are commonly referred to as failure points.


When I got it all put back together yesterday I hopped in the car and said a little prayer before starting it but that I didn’t completely bork the ECU. It fired up and acted test drives not showing any of the same symptoms. It isn’t randomly cutting out and dying on me.

Of course that doesn’t mean I’m done with things. After I fairly lengthy test drive and it got up to operating temperature it started stalling out when going back down to idle if I had the AC on. Turning the AC off solved the issue so that is something I’ll need to figure out there. Either a vacuum leak or some idle issue.


I’ve also done some more investigation on the fact that it is an automatic to manual conversion. There are definitely some things that are mentioned in the Bentley manual for my here 535i that are different from an automatic and a manual. I’ll have to go through and see how thorough the conversion was. I know one thing I need to change is a shift boot. It doesn’t completely go all the way up to the shift knob, so hot air comes up that area while driving.

With the safety inspection done I’ll go and do title and registration this week so all of the paperwork is out of the way.


Now to start the real list...