Here's some information posted a long time ago by C.D. regarding the US 1974 2002tii fuel injection and distributor. My 1974 tii still retains all of the stock setup (injection pump, distributor and vacuum limiter valve).
(on the air cleaner housing)
1974 2002 tii emission control changes:
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" To reach more favorable control of HC (hydro carbons / unburned gas) during coasting (during high manifold vacuum), the air filter and the intake manifold were connected by an air-hose in which is interconnected a vacuum limiter.
The valve is controled by vacuum and connected to the vacuum line between the intake manifold and the vacuum unit of the distributor. At high vacuum , the valve opens the air-hose fully. "
FUEL INJECTOR PUMP WITH MODIFIED IDLE ADJUSTMENT:
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"In conjunction with the described vacuum Limiter Valve, the fuel injector pump got a new idle adjustment. During coasting (closed throttle butterfly), the pump injects a small amount of fuel and produces in connection with the air through the Limiter Valve an air mixture. This fuel injector pump has the factory type number
92 004 020
PL04 - 124.02.A1
on a plate at the left side of the housing.
These injector pumps are not exchangeable with hitherto existing injector pumps."
MODIFIED IGNITION DISTRIBUTOR WITH VACUUM RETARDER:
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"The ignition distributor was replaced by a new type with vacuum retarder. The factory type is
0231 180 013
The ignition timing is 25* BTDC at 2,700 rpm. During adjustment, disconnect the vacuum hose from the distributor vacuum unit."
Dwell angle 60*
spark plug gap 0.024"
idle speed 850 ...1000 rpm
information from BMW of North America Emission Control Training Manual 6/1978
part number for the Vacuum Limiter Valve is 11.74.1.259.110 (No Longer Available)
testing of the valve should be easy using a hand vacuum pump and checking for leakage
happy trails,
Creighton Demarest
Darien, CT.