Volvo CFI system

[Steve Jernigan]

Hi Group !
	Hope someone can help. This is not really an EFI question, the old Volvo
240 (1977) uses a continuous mechanical fuel injection (CFI) system, but
this one has an O2 sensor and what the manual calls a "frequency valve"
which apparently adjusts the mixture in response to the sensor. After
260,000 trouble free miles, the ol' tank no longer passes emissions for
hydrocarbons, this accompanied by a slightly rough idle. CO is just fine,
~1%. Compression is OK, 120lb - 130lb, all new ignition parts, tried
swapping in different distributor, coil, CDI box, O2 sensor, disconnected
evaporative emissions, checked fuel pressure, injectors and cold start
/fast idle components, and finally pulled and cleaned the entire air valve
/ fuel regulator assembly (a real pain BTW). Same stinkin' problem.
	I have observed that disconnecting the "frequency valve" seems to smooth
out the roughness in the idle, but lack the electronics to test the HC
emissions under these conditions.
My question is, then, does anyone have any information regarding this
proto-EFI system, or any other thoughts which might help get my beloved
Swedish tank back on the road for the next quarter million?

	Thanks in advance! 
	Steve Jernigan, 
	University of Colorado,
	Microelectronics Research Laboratory.

PS, Has anyone successfully reverse engineered the original Holley analog
throttle body fuel injection? Sure could use a schematic for the control
box, and Holley isn't very helpful at all.
TIA, again! S.