[rfmaster]

Originally Posted by benntn

Everyone is right there is no O2 sensor on mine. I read in the Haynes that it is on the manifold for 8v's but never says Cali trucks only. So I looked again and there isn't one on mine. So now I've been testing the EFE "heat riser" value and it appears to not be opening own its own. It's either the temp switch or the heat riser value. When I try to move it by hand its very hard to open. If I use a screw driver, I can open the value. I've replaced the vacuum hose but i can't tell when i remove it if there is vacuum or not. Is this why I'm failing emissions test?

Actually EFE (Early Fuel Evaporation) can be considered one of the most lame ideas that GM came up with before fuel injection. The EFE bolts to the right exhaust collector. EFE is flapper valve - designed to restrict exhaust gas flow when coolant temperature is cold forcing instead exhaust to flow through intake manifold exhaust cross over passage. In grand scheme of things it should result in faster warm-up. Once warmed - the vacuum control switch would shut off vacuum and spring loaded EFE would move to a fully open position. I had one of these things on '76 305 Chevy Malibu - never worked right as spring and vacuum control modulator were flaky (and that was 20+ years ago).


//RF