Vacuum drops when turn on a/c
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Model: Cherokee
Vacuum drops when turn on a/c
I have a 93 grand cherokee 6 cylinder laredo. The vacuum on the intake manifold is a steady 17 psi at a warm idle. Thing is when I turn on the air conditioner a/c the vacuum drops by 3 psi to 14. This seems to cause the motor to idle rough though the idle does NOT decrease in RPM's. I can not figure out what the connection between turning on the a/c and a drop in vacuum pressure is. Checked all the vacuum lines, just about every single sensor has been replaced by me over the last few years.
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#3
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Year: 1995
Model: Grand Cherokee
Engine: 4.0 with all of the noise and clatter
When the A/C compressor kick on, the idle air control motor opens a little to raise the RPMs up for the load of the compressor. There is your slight decrease in vacuum. The compressor may be getting a little old and drawing more power from the engine causing the rough idle. Do not add oil to the compressor, as stated above.
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Year: 2004
Model: Grand Cherokee
Engine: 4.7L V8
When the A/C compressor kick on, the idle air control motor opens a little to raise the RPMs up for the load of the compressor. There is your slight decrease in vacuum. The compressor may be getting a little old and drawing more power from the engine causing the rough idle. Do not add oil to the compressor, as stated above.
Dan
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