I am trying to identify where the vacuum hose goes to. It is one that is full time vacuum and it is on the port in the rear of the q-jet base. Right next to it is the big one where the brake booster plugs in (just like the big one in front where the PVC valve plugs in...).

The line is a hard plastic line that goes from the q-jet to somewhere behind the engine so I cannot see really where it goes. I have been told that there isn't one that goes to the 700R4 stock, but I want to know if it was added to go to a vacuum switch when the shop put in my rebuilt 700R4 about 3 yrs ago. Any ideas?

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1984 z28 w/ a 357 cu in. monster engine which is looking like the posterchild for Edelbrock... all the suspension stuff... 9-bolt posi disk is in... K&N filter... 93 octane...

-=ICON Motorsports=-

 

Biochem, there are no vac. lines going to the 700R4 on my 84 Z28. The hard plastic vac. line that you refer to goes to the Differential Pressure (vac.) Sensor (DPS). The DPS is a vac. sensor that measures the differance in atmospheric pressure and intake manifold vac. The DPS sends a voltage signal to the ECM. High vac. = a high voltage sig. Low vac.= a low voltage sig. I think you get the pic. Now what does the ECM do with this voltage sig. you ask?? Well i will tell you. If the voltage sig. is high (5v) the ECM will increase the spark adv. and a low voltage sig. will reduce spark adv. If the DPS sees less then 10" of vac. the CEL will come on after a certin period of time(i don't know what it is)and you will get a code 34. If you install a wild cam and your vac. at idle is below 10" you will have this proublem. I hope this helps?

-Auggie-

 

That makes sense! Thanks.

 

My Q-jet has a line real close there that goes to the vacuum actuator for the air door on the secondaries.
Later,, Matt