I have been working with the 87 factory manual to run though the tests and adjustments. Currently, I discovered that both T.V.V. (thermal vacuum valve) appear bad.... but there's a little confusion. I'll describe where I am here:
Both TVV's appear identical and are original to the car. They have 2 vacuum ports and screw into the water passage of the intake manifold on the driver's side of the carb. They are grey/white in color and both have K6J08 stamped on. There's also a "VT 1 3" on one and "VT 0 4" on the other (the numbers are near microscopic and each are in an individual round recess). I removed these TVV for cleaning and inspection and found they just open and close the vacuum access due to water temp. No direct connection to the intake at all. That comes from 2 other manifold lines that connect to the TVV.
1st TVV on pages "EF & EC-159" and "EF & EC-162" works with the idle controls and failsafe system. The spec says the valve is "off" below 30 C or 86 F. I assume this means the valve should pass no air at 70 F room temp. By sucking and blowing either port, it easily passes air, so it's bad. This accounts for the 3000 RPM cold idle and maybe 1600 RPM warm idle if the vac lines are attached.
2nd TVV is more involved. The vacuum diagram on "EF & EC-132" shows it allows the EGR vacuum and Air Injection vacuum. Obviously, this involves a rich condition if not right. On "EF & EC-181" there's also a TVV allowed connection to the air cleaner that states "TVV lets vacuum leak during cold condition (below 140 F), so that the opening of secondary throttle valve may delay, and thus improve driveability." Now this TVV is working exactly as the 1st with no air stoppage at all at the ports. So, is it supposed to be "off" at room temp like the 1st and open above 86 F to satisfy the 140 F spec???
OK, one last wrinkle. The replacements are supposed to be Nissan numbers 14890R and 14890M (this last one now 14890-V0500) in the parts book diagram. They are not to be found as NOS that I can see online (though maybe at dealers). I can find an identical appearing "Ported Vacuum Switch" as Duralast E988 and Standard PVS90. I have no idea if these have right operation for me.
Now, as emissions only require a warm engine for tests, I could disable a lot of this vacuum spaghetti and just hope to make it work "looking" right. But I'd like to do a proper job if I can.
