This has been by far the most challenging thing to tame to date. I walked away from the engine bay confused a dozen times. I bought a tuning manual. I read it. I implemented changes. I fixed many issues. But after repairing one issue after another, the central issue of the engine bogging under any load over 1800rpm remained.
I was going mad. Here’s a list of everything I repaired or replaced:
- Fully disassembled the carburetor and soaked and cleaned each part.
- Replaced the throttle shaft bushings (they were brittle and brown
- Replaced the gaskets
- Re-jetted according to guidance on BMW2002FAQ (the jets were wildly far from stock)
- Replaced fuel lines and in-line filter
- Replaced fuel pump
- Replaced throttle linkage
- Cleared fuel accelerator pump channels and un-stuck check valve (twice)
Each of these things needed to be done and each of the changes did show some sort of positive improvement in engine idle general performance. BUT THE ENGINE STILL BOGGED UNDER LOAD.
I was completely baffled. I was literally out of ideas.
July 6th, 2024
We had been at my cousin’s house in the Iowa countryside celebrating the Fourth with some food and drink. We got home relatively late for us these days, around 10:30pm. My wife drove, I’d had a few beers.
When we got home I held off on going to bed. I grabbed a beer and stood in the garage. I just stared at the carburetor, almost angrily. I don’t turn wrenches after a few beers. But earlier that day I’d removed the top of the carburetor, I suppose so I could stare at it and scratch my head.
So that night, as I stared angrily at that partially disassembled carburetor, I began thinking about the auxiliary venturis. Earlier, when I’d disassembled the carb to clean it, I wasn’t able to get the auxillary venturis out of their slots. They in there so snug that I assumed they weren’t to be removed.
Then I looked at the images in my Weber shop manual. THE AUXILLARY VENTURIS CAN BE REPLACED. That means they can be removed. That means they might be installed incorrectly.
So I started wiggling one. Eventually it started to work free. Then I got it out. It was installed upside down. I almost cried tears of joy. I knew immediately that this is what I’d been chasing. Six weeks had passed! I was chasing this for 6 whole weeks.
I installed both of them correctly. The next morning I drove the car for the first time. It was glorious.
