Firstfives.org

Apparently whatever the thermovalve does ( green plastic deal the vacuum hoses from the throttle body to the distributor enter and exit ) ( $136.00 ! OEM) it cares which tube goes where.

Tube from throttle body goes to the outside, tube to the distributor uses the middle pipe. Leastways, switching the tubes to that configuration seems to have helped make the throttle far less jerky letting off.

Having done that ( copying my '79 ), I timed it back to 2200 rpm, ball centered, vacuum line plugged. Still not fully participating in instant, neck snapping, floor it, go, throttle response but much better.

Sure are a lot of weeny teeny details that all need to be right. Accent on taking notes and / or photos whenever taking things apart.

Look at 11 71 054 Replacing Thermo Valve under Engine 11. There is a testing procedure.

http://www.bmwtechinfo.com/repair/main/057en/index.htm

It is my understanding that this valve is a vacuum advance limiter, so designed that the engine could not receive maximum advance from the distributor until it reached a specified temperature. Translate = Kleinpeter didn't want you to be able to wear out your engine by flooring it when cold, so advance only comes into play during warmup from the centrifugal advance weights mechanism under the impulse sender in the distributor.

It is also my understanding it is only a vacuum 'switch'. 'On' above a certain coolant temp., 'off' below. You can pull it out, put it in the freezer for a short while and air should not pass through either orifice. Heat up some water in a cup in the microwave and sit it in there. It will open when ready with a surprising 'pop' and air will pass through the orifices. I don't think it matters which hose goes to the distrubutor or which one goes to the intake orifice.

Frustration alleviation 101 - Just know that by your chasing this problem, you are learning more about your engine and its management devices than you ever knew. I learned all this stuff this way chasing my warmup poor idle condition for years.

Happy learning, best of luck.

Wrong. I'm learning because there's a you teaching me. Otherwise I'm just switching things around without knowing why.

Glad there's a testing procedure. Mine works, but new are $130 listed on realoem.com. A dab spendy without testing dead first.

Rats. I was hoping the lines mattered and I fixed by switching them. Must just have been psychological, or lunar magnetic fields