86 suspected vaccum problem
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More Turbo
Joined: Aug 2005
Posts: 683
Likes: 6
From: North Georgia
86 suspected vaccum problem
Here is what is going on. When I am driving down the road and have the air conditioning on and come up on a hill (making engine work harder) the air that is blowing out the a/c vents goes away and will return after i get over the hill. I suspect I am losing vaccum or I just dont have enough. I have a 460 with all the smog stuff gone and I am getting vaccum from a port below the pcv valve at the passanger side valve cover. Is that a good location to be getting vaccum or should I be getting it from maybe the intake behind the carb. any ideas??
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More Turbo
Joined: Aug 2005
Posts: 683
Likes: 6
From: North Georgia
it has a check valve and the canaster you are speaking of. Is the vaccum source from the valve cover good enough or even the right source to be getting vaccum from?? I will hook up a guage and see if it will hold vaccum or should it hold it?? what kind of numbers should I test for??
Posting Guru
Joined: Jun 2004
Posts: 1,635
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From: Niceville, FL.
On my '83 the vacuum source is an intake manifold fitting (at rear) with a line going to a Vacuum Distribution Block (VDB) which is essentially a "Tee". From the VDB a line to the Heat & A/C circuits (check valve, reservoir, control) and another to the automatic transmission (if so equipped) vacuum modulator. My PCV valve does not have a vacuum line. So, I'd connect the vacuum check valve such that manifold vacuum is directly applied.
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Joined: Nov 2004
Posts: 4,901
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From: Salt Lake City, Utah
To some extent, this is normal function. However, anything that causes a drop in vacuum pressure can cause this problem. One possibility, is a clogged catalytic converter. The backpressure from a clogged cat will cause lower than normal vacuum. I'm not saying you should immediately jusp to the conclusion that a clogged cat is the problem. But it is a possible problem or contributor that should not be overlooked.
