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Engine vacuum diagrams please?

Tiny
DRJEFFCOYLE
  • MEMBER
  • 1997 CHEVROLET TRUCK
The pcv hose on the driver side of the 5.7 liter engine connects from the valve cover to the intake manifold. There is another smaller vacuum line that comes from this connection at the intake manifold. Where does this vacuum line connect? On the passenger side of this same engine, there are 3 hoses/lines that connect to the evaporation emissions purge solenoid vacuum switch. One to the canister purge solenoid, one to the purge fitting at the vapor canister, but where does the third vacuum line coming off this device connect to? No vacuum diagrams show these 2 lines.
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Sunday, December 7th, 2008 AT 10:46 PM

19 Replies

Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Here is the vacuum diagram for your car (BELOW). The 3rd goes to the fuel tank, the smaller hose goes to the MAP sensor. There are not many lines. I was unsure to give you the answer because its V8 and there's 2 different engines and the vacuum diagrams are different-I can provide the other diagram if you wish-hoping its the one you're looking for.
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Monday, December 8th, 2008 AT 5:57 AM
Tiny
DRJEFFCOYLE
  • MEMBER
  • 2 POSTS
Thank you for the vacuum diagram they helped me and I got the truck running great.

Thank you.
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Wednesday, December 10th, 2008 AT 5:33 PM
Tiny
THIS IS MIKE
  • MECHANIC
  • 686 POSTS
Our techs work hard to try to diagnose thousands of problems. Automotive repair is something we are very accurate with, sometimes it requires cooperation back and forth to get to the solution.
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Thursday, December 11th, 2008 AT 12:37 PM
Tiny
COCONUT9
  • MEMBER
  • 2 POSTS
  • 1997 CHEVROLET TRUCK
  • V8
  • 4WD
  • AUTOMATIC
  • 157,800 MILES
Have a 1997 5.7 liter V8 stepside pickup. Symptoms include high idle while running down the road, 40mph and release gas pedal and truck very slowly lowers in speed unless brakes depressed then it slows the engine idle down. examination shows a vacuum line port with no hose and I cannot determine what (if anything) should be in there? I have never replaced the MAF or serviced it in the last 6 years that I know. Dont know where to start or where to get a diagram to check the hose issue. Is there instructions on cleaning or replacing the MAF, or replacing the thermal sensor they speak of myself? Hard to justify another expensive dealer visit for this old but dependable truck. Will ADD a tip and another donation for a good advised solution - first time user. I have a picture to upload. [added: ALSO there is pressure in gas tank when gas cap is removed, hisses significantly when opened to fill - maybe related??


http://www.2carpros.com/forum/automotive_pictures/556948_DSC04160_1.jpg



http://www.2carpros.com/forum/automotive_pictures/556948_DSC04161_1.jpg

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Sunday, April 25th, 2021 AT 2:31 PM (Merged)
Tiny
FACTORYJACK
  • MECHANIC
  • 4,159 POSTS
There is no hose that goes to that solenoid, it is a vent. The solenoid you have pictured is the evap purge vacuum switch, I believe the one next to it with the red connector is the evap purge solenoid. Here is a brief description of its purpose. A vacuum switch in the purge line detects when the system is purging. The normally closed switch will open when less than 1 inch Hg is present in the purge line.

Pressure in the gas tank is not necessarily an indication of a problem, it can be considered normal. The MAF can be cleaned by spraying the hot wires with an electronics, or contact cleaner aerosol. If you had an active vacuum leak, you should have an engine light and corresponding lean fuel trim codes
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Sunday, April 25th, 2021 AT 2:31 PM (Merged)
Tiny
COCONUT9
  • MEMBER
  • 2 POSTS
So you are syaing that a vacuum leak is probably NOT this issue and not causing the high idle situation?
It does not seem to be a sticky throttle cable or anything - once vehicle is slowed to a stop at a light, the engine slows down with it. Perplexing.

I see in another post there is an idle controller. With no codes present, is there a way to test that unit? So far, I have not located it. It must be deep inside the black plastic top works.

I do not see any idle adjustment screw (you are probably LOL)

Thanks Coconut Chuck
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Sunday, April 25th, 2021 AT 2:31 PM (Merged)
Tiny
FACTORYJACK
  • MECHANIC
  • 4,159 POSTS
There is an idle air control valve on the RH rear of the throttle body. Aside from replacement, the only other thing is to remove it and clean the passage. It can develop deposits. It's wire colors are green/white, green/black, blue white, and blue/black. There is a service procedure for rough, unstable, or incorrect idle. It is pretty generic in nature. It is included.
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Sunday, April 25th, 2021 AT 2:31 PM (Merged)
Tiny
JASON.MOIT
  • MEMBER
  • 1 POST
  • 1986 CHEVROLET TRUCK
  • V8
  • 4WD
  • MANUAL
  • 154,000 MILES
I have a 86 chevy pickup with a 305 that will not idle. I think I might have reversed some vacuum lines but I can't rad the diagram on the truck. How can I make sure my vacuum lines are in the correct places
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Sunday, April 25th, 2021 AT 2:33 PM (Merged)
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Here are the vacuum hose routing diagrams for you truck. Check out the diagrams (Below). Please let us know if you need anything else to get the problem fixed.
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Sunday, April 25th, 2021 AT 2:33 PM (Merged)
Tiny
CAUSTIN86
  • MEMBER
  • 1 POST
  • 1986 CHEVROLET TRUCK
I am rebuilding this truck and can not find a diagram or picture of how to do the vacuum line or hose. It's a 1500 Scottsdale. Also I need to know how to fix the Eldon Brock Carburetor. It's a 1600 or 1200
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Sunday, April 25th, 2021 AT 2:33 PM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
I don't understand how you want to fix your carb which is an edelbrock I beleive. Here is a vacuum diagram but it is for a federal emmission not california..


https://www.2carpros.com/forum/automotive_pictures/406719_vacuum_diagram_1.jpg

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Sunday, April 25th, 2021 AT 2:33 PM (Merged)
Tiny
RUFAS
  • MEMBER
  • 2 POSTS
  • 1984 CHEVROLET TRUCK
  • 5.7L
  • V8
  • 2WD
  • AUTOMATIC
  • 65,000 MILES
I am looking for XHH vacuum line diagram for a California 1985 Chevrolet C20 Build date of11/84. 5.7 with a automatic transmission.
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Sunday, April 25th, 2021 AT 2:33 PM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
See attached pic xhh is 1984 not 1985 85 is uhh but that is for a diesel.
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Sunday, April 25th, 2021 AT 2:33 PM (Merged)
Tiny
RUFAS
  • MEMBER
  • 2 POSTS
HAMC
Thank you, I could not locate that diagram. That's why I also listed the build date. All info. I found pointed to this being a 1984 code, thank you again.
Rich
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Sunday, April 25th, 2021 AT 2:33 PM (Merged)
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
Please let us know how it turns out
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Sunday, April 25th, 2021 AT 2:33 PM (Merged)
Tiny
SCORPEON40
  • MEMBER
  • 33 POSTS
  • 1982 CHEVROLET TRUCK
  • 4.8L
  • 6 CYL
  • 4WD
  • MANUAL
  • 190,000 MILES
I wish to make sure my vacuun lines are ran correctly could you share a resourse or two of a diagram of the vacuum routing. Thanks ahead of time !
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Sunday, April 25th, 2021 AT 2:33 PM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
See pic it's for a 4.1 or 250- 6 cylinder they did not put a 292 in it so hook it up the same.
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Sunday, April 25th, 2021 AT 2:33 PM (Merged)
Tiny
SCORPEON40
  • MEMBER
  • 33 POSTS
  • 1982 CHEVROLET TRUCK
  • 4.8L
  • 6 CYL
  • 4WD
  • MANUAL
  • 190,000 MILES
I have questions of weather my vacuum lines are routed correctly could you send me a resource thanks ahead of time.
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Sunday, April 25th, 2021 AT 2:33 PM (Merged)
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
I found this for the 4.8L.
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Sunday, April 25th, 2021 AT 2:33 PM (Merged)

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