My 1993 California Loyale passed smog for every test except it was 3pts high on the low-speed hc test. I have an SPFI, 5speed, with 180k miles on the car. I noticed the fuel pressure regulator vacuum line has zero vacuum at idle and when I rev the engine! I blew some air into the passage and it only exits from a port ABOVE the throttle plate! According to theory, it's supposed to get manifold vacuum below the throttle plate so it can actuate at idle to reduce fuel. So why is it ported to above the throttle plate at atmospheric? What's funny is I don't have any idling or other problems associated with a faulty fuel regulator, yet it appears it's not doing anything. The shop manual shows the SPFI engine has the port above the throttle plate too. However, it's below the throttle plate for the MPFI engine!
Anybody have an explanation for such a strange setup? Is the regulator in the SPFI just a 'fuelish' invention in this case?