Vacuum diagram for 84
Thread Starter
Racer
Joined: Sep 2004
Posts: 317
Likes: 1
From: 84 Blue A4 Garrison Ky
Vacuum line diagram for 84
I am need of a vacuum diagram for my 84. I am trying to replace all the old dried brittle vacuum lines on my 84. A couple of the lines were not connected so a diagram would be a big help. I have a service manual but it is no help.
Last edited by DRAKEFAMILY2; Oct 6, 2004 at 08:42 PM.
Race Director
Joined: Sep 2000
Posts: 17,298
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From: The Top of Utah
My parts book doesn't show either the diaphragm or a repair kit. From GM, all you can get is a complete power brake booster, pn, 14046849. You might check with some auto parts stores to see if they offer repair kits.
RACE ON!!!
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Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Over on the C4 General Discussion section, there is a thread titled "FREEBIE". There is a free download of the '84 service and electrical manuals, available. Since you already have the service manual, I doubt this will be much help to you.
RACE ON!!!
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7th Gear
Joined: May 2026
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Hey, I know it's been like 18 years but what did you do to fix the idle? I'm chasing an idle at 1.3-1.4k rpm that may be vacuum leaks or may be ECM related.
7th Gear
Joined: May 2026
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I was actually trying to find what size vacuum line the car used when I found this thread since my map sensor line was pretty bad and dropped the idle by 200rpm when I changed it. So I was hoping the OP would somehow see my reply after so many years of being inactive lol.
The only vacuum leak I know of currently is I found the car decided to eat the oil pan gasket by the rear main seal somehow after I had just replaced it with a nice felpro one.
If you've got any input that would be greatly appreciated
Pro
Joined: Jul 2023
Posts: 525
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From: Marysville WA
Some of the less obvious places to look are the felt gaskets around the throttle bodies that the air cleaner lower half sits on. Mine were missing when I purchased the car, and the vacuum line from the cruise control to the brake light switch. Mine was very rotten at the switch. I also replaced the three way check valve that is shared by that hose and the one going to the vacuum ball near the left headlight.
7th Gear
Joined: May 2026
Posts: 7
Likes: 0
Some of the less obvious places to look are the felt gaskets around the throttle bodies that the air cleaner lower half sits on. Mine were missing when I purchased the car, and the vacuum line from the cruise control to the brake light switch. Mine was very rotten at the switch. I also replaced the three way check valve that is shared by that hose and the one going to the vacuum ball near the left headlight.
The car does idle higher when I press the brake pedal "too far" and some days I can hear vacuum bleeding off even when I barely tap the pedal and have basically no power brakes. So I'll probably replace the brake booster aswell, but when I unplugged it entirely and plugged the line it still idled the same.
Pro
Joined: Jul 2023
Posts: 525
Likes: 274
From: Marysville WA
Xfireperformance.com has a very useful FAQ section. Check out answer #20
https://www.xfireperformance.com/faqs
https://www.xfireperformance.com/faqs
7th Gear
Joined: May 2026
Posts: 7
Likes: 0
Xfireperformance.com has a very useful FAQ section. Check out answer #20
https://www.xfireperformance.com/faqs
https://www.xfireperformance.com/faqs
Pro
Joined: Jul 2023
Posts: 525
Likes: 274
From: Marysville WA
The top diagram reminds me that there can be vacuum issues if the top plate on the intake manifold has some loose bolts or a leaking gasket. Try re-torquing the bolts in the order of the red numbers first and see if that does anything. 15-25 lbs torque. Some have mentioned going 15-20-25 increments.