I recall my surprise at analyzing some 3-series E30 glove boxes, and discovering that the glove boxes for cars with the later-than-Motronic-1.0 computer had a shallow notch at the inner front corner, so that the thicker fuel injection cable (three rows of pins vs. the earlier two) doesn’t chafe. It’s a very logical engineering change, and not surprising. The glove box with the notch even has a different part number.

What made this surprising is that the official BMW parts list mentions only one variation. So, by analyzing the parts, physically, carefully, in person, I found out more than if I’d just read about things online.

For a while, I tried to figure out what made some cars have the earlier-style glove box vs. not. The change seemed to center around 1987 but I couldn’t put my finger on it until I realized that cars with the older version of Motronic computer had the older version of glove box, and 1987 was the year when things changed a lot as such — but the 1987 325i cars had the newer-version computer whereas the 1987 eta-engined cars still had the older-version computer.

This experience really inspired me to go look in person at what’s actually going on. It reminds me of when I worked at an automobile assembly plant (not for BMWs, sadly). The production control folks had recently managed a change by which cars of a particular model would be fitted with chrome tips on their exhausts. The parts were ordered, brought to the production line, and the assembly instructions were changed to tell workers to put the chrome tips on. But, at the end of it all, my job included being the reality-check person, to go see if in fact all of this planning had actually resulted in chromed-tip exhausts on cars exiting the assembly line. For me, there’s nothing as solid and reassuring as seeing something first-hand.

So, today’s project involved Mass Air Flow Meters on the M30 engine. I own a 1980 BMW 633 CSi, a 1992 BMW 735i, and several models in between, including a 1984 BMW 633 CSi and a 1984 BMW 733i. My tech and I inspected the mass air flow meters on all of these cars, and checked the part numbers. Of course, it’s possible that some of these parts were not originally on the car, but I’ve personally driven each of these cars so I know that the part at least works on that car.

Although the 1992 car has a pretty plastic cover on top of the mass air flow meter, when the cover is removed, the part is the same as on all the other models we analyzed. And so, now we have a good handle on mass air flow meters for the M30 engine.

There are still a million things we DON’T know for certain, but it’s nice to have a fairly good handle on at least this tiny part of the puzzle.

That’s the sort of confidence and certainty that we enjoy.