Hey guys, I just noticed a vacuum line that runs from my firewall on the passenger side to a little canister behind the smog pump is broken in half... anyone have any idea what this line does and if it's bad to leave it like that?? thanks. btw this is for my 88 gt.
It's to help vent your emissions system. Really, you won't notice a huge difference with it not hooked up other than the vacuum leak and maybe the exhaust smelling a little worse.
Sounds like the diverter valve for the smog pump. If the valve is non fuctional, the catalytic converters don't get the air they need to function properly. Over time, they will gather carbon & sludge and restrict the exhaust system.
If you don't have cats, don't worry about it.
The following code description helps with understanding how it works...
Codes 94 & 44 - Check vacuum lines for leaks, & cracks. Disconnect the big hose from smog pump: with the engine running you should feel air output. Reconnect the smog pump hose & apply vacuum to the first vacuum controlled valve: Its purpose is to either dump the pump's output to the atmosphere or pass it to the next valve. The next vacuum controlled valve directs the air to either the cylinder heads when the engine is cold or to the catalytic converter when the engine is warm. Disconnect the big hoses from the back side of the vacuum controlled valve and start the engine. Apply vacuum to the valve and see if the airflow changes from one hose to the next.
The two electrical controlled vacuum valves mounted on the rear of the passenger side wheelwell turn the vacuum on & off under computer control. Check to see that both valves have +12 volts on the red wire. Then ground the white/red wire and the first solenoid should open and pass vacuum. Do the same thing to the light green/black wire on the second solenoid and it should open and pass vacuum.
Remember that the computer does not source any power, but provides the ground necessary to complete the circuit. That means one side of the circuit will always be hot, and the other side will go to ground or below 1 volt as the computer switches on that circuit.
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