93 astro 4.3(w) vent, ac vacuum problem

Yes, I myself am having the ac air out of the defrost and heater out lets

I have read alot here about vacuum lines however since I have a 4.3 code (w) with CPI 1993 astro i think the vacuum lines may run differently here on this model. where as the most info here may be for 4.3 tbi,

any way where is it that this model has these vacuum lines since I cant find them where they should be as discribed on other post

in the back of the engine there is a out let which has vacuum and a rubber hose is pluged in than then gose to a round vacuum tank ball and from their the line continues up to a the frame and across the wiper area and then near the drivers side area it looks like it goes thur the fire wall and into the heater control knobs
where would I look to find the leak

air does blow but under aceleracion it loses it and the air drops to the lower vents

any help i would appricatet

thanks

Robert

Just found my issue similar to yours. The vacuum line runs from the passenger side where the tees are in the lines. There is one line that comes across from the passenger side and crosses under the air intake pipe behind the mass air flow sensor and connects to a port on the top of the engine on the drivers side. This is hard to reach behind the air conditioning pump.

The issue is in the plastic lines. Chevy uses a rubber to plastic combination of hose in these hoses and the plastic gets brittle. Replace the hose with all rubber and get rid of the plastic. This is the primary vacuum feed to the heater system controls.

Remove the air cleaner assembly and the mass air flow sensor and you will see the air intake tube. If you remove this to the next joint it is easier to work in the confined area. With this open you will see the rubber/plastic vacuum line where it crosses over. Replace the line from behind the a/c pump to the a/c condenser area tees. There are several plastic lines in that area as well. You may want to check them and replace with rubber lines.