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Vacuum line stalling engine when connected to nvld

2486 Views 48 Replies 5 Participants Last post by  Bob Lincoln
Does anyone know why when I connect the 2 vacuum lines 1 from plenum the other on to of throttle body the engine cuts off on idle.
Do these lines go to a vacuum pump? Defective?
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. . . Does anyone know why when I connect the 2 vacuum lines 1 from plenum the other on to of throttle body the engine cuts off on idle. Do these lines go to a vacuum pump Defective? . . . .
As ImperialCrown stated we need to know specific make, model, year and engine configuarion, 4 cylinger, V6, V8, and some images of the vacuum lines in question to make a reasonable, accurate diagnosis.

Now if you wanted a "wild guess" I would say one of the suspect vacuum lines might be connected to the EGR valve. Fully activated EGR (exhaust gas recirculation) will stall an engine and stop it from idling. But again just a guess. Give more detailed information as requested.
 

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Ufortunately some of the drawings in a factory service manual are mislabeled. In post #6 presented by ImperialCrown the trapezoid symbol that is labeled 2.7L would make you think that symbol represents the engine. It should be labeled as the vapor canister. See attached image.

Rectangle Font Parallel Schematic Auto part


. . . .the "pump" he is talking about is the NVLD pump and it's below the master . . . .
The device that provides pumping action and applies a vacuum to the fuel tank and evaporative system is the purge solenoid that is mounted under the power brake booster. The NVLD device vents over pressure, cleansed air to the atmosphere and seals the tank under a vacuum. It is located along with the vapor canister at the fuel tank.
 

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. . . . .Standard 4 cylinder stalls on idle when pvc valve hose connected to plenum or the vacuum line on top of throttle body. Disconnecting either one did not stall.
This car does not have egr valve, seems the 2 vacuum hoses, one back of plenum and other on top of throttle body, goes back to the fuel line and the nvld canister. Does anyone have ideas . . . .
It is difficult to envision the dislodged. vacuum hoses on your vehicle without an image. If you can take a picture and post that would be helpful. Otherwise find the underhood vacuum diagram and connect lines as shown.

From a view into the engine compartment all you will see is the purge valve under the brake booster. There will be a vacuum hose from the purge valve that connects to a line under the body that runs to the vapor canister mounted on the fuel tank. The purge valve will have another port with a vacuum line that attaches somewhere on the intake plenum.

Follow the larger hose from the brake booster to the intake system. At the intake is there an open port with no vacuum hose attached? If YES this port with missing hose should have to be connected to the purge valve.

This connected vacuum line should agree with the underhood diagram. If the engine stalls at idle with this configuration, it is possible that the purge valve is stuck open. With a stuck open valve the engine is drawing in rich fuel vapors and the overly rich air-fuel ratio is causing engine stall. Just a guess on my part.
 

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. . . No hoses are missing, ask the hoses are connected you the correct ports , how can I test the purge valve . . . .
Start engine and let it idle. Remove vacuum hose connected to vapor canister port on purge solenoid valve. Apply piece of paper to uncovered port on valve. There should be no vacuum at port trying to attract paper with engine idling. If vacuum is found, the purge valve is leaking and needs to be replaced. See attached image.

Font Camera accessory Machine Auto part Engineering
 

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. . . .Cannot blow through the tube, this tube goes to the valve below the brake booster, in a real awkward place, I guess this is the canister. The purge valve on the throttle body is ok, since I changed that already . . . .
As ImperialCrown stated in post #26 the device with vacuum hose below the power brake booster is the purge valve. It is not the vapor canister which is located at the rear alongside the fuel tank. Please post a picture of the attachment of the vacuum hose at the throttle body and the device you changed at the throttle body.

. . . .I also came across a relay,/fuse yellow and orange in color, 3, pins that fell off and I cannot find where that plugs into, wondering if that had something to do with it . . .
Please post a picture of this "relay / fuse yellow and orange in color 3 pins that fell off ". Identify any wire colors attached including secondary tracer color wire.
 

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. . .I give up, all the vacuum lines are connected correctly, no kinks or tears, installed new nvld valve and engine still stalling, even changed purge valve on throttle body. . . .
The purge valve is NOT located on the throttle body. What device have you changed on the throttle body? Have you changed the throttle position sensor? Idle air control? See attached image.
Slope Organism Font World Parallel


. . . .did the ac lines have something to do with these vacuum lines. . . . .
Air conditioning refrigerant lines would not cause this issue.

. . . If the charcoal canister is flooded with liquid gasoline, it may stall the engine by being too rich. It is supposed to store fuel vapor only. . . . .
I would think that even if the vapor canister is flooded with liquid fuel and the purge valve is sealing correctly, no liquid and / or vapor should be entering the induction system through the purge valve???

Have you check the PCV (positive crankcase ventilation valve)? If it is stuck open it would allow excess air and crankcase vapors to enter the induction system and cause a stall at idle. Remove the hose at the PCV valve and seal the end. Does the engine continue to stall? Remove the PCV valve from the camshaft cover. You should be able to shake and hear it rattle. If no noise or movement detected it is stuck and needs replacement. See attached image.
Font Parallel Illustration Sleeve Screenshot
 

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. . . .I changed the throttle position sensor . . . ..
You probably installed the TPS / throttle position sensor incorrectly. There are plastic lugs in the TPS which must be mated properly to adjoining lugs on the throttle blade shaft. If not mated properly a rotating throttle blade shaft will not advance the TPS and cause a varying TPS signal to be sent to the PCM. An accurate TPS signal is necessary to allow the engine to run properly.

Review this video which shows how to replace a TPS. Video is for a V6 engine but the technique for proper installation is identical for a 4 cylinder engine. Pay particular attention to the video starting at time interval 2:50. It shows the lugs on the TPS which mate with lugs on the throttle blade shaft.

 

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. . . Here is the picture, has 3 pins . . . .
I believe the image shows a 40 amp cartiridge fuse used in the PDC / power distribution center or fuse box in the vehicle. Orange is the convention color used for 40 amp. The PDC is located under and to rear of air filter plenum box. Is number 40 printed somewhere on the fuse?

Remove the lid and see if a cartridge fuse is missing. There is a provision for holding a spare fuse in the fuse box. See attached image for identification of components in PDC.

Schematic Parallel Font Rectangle Technical drawing
 

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. . . This is a different fuse, but I looked in the fuse box there's a fuse missing that's 40amp, days for abs pump, could this be the booster not sucking in air. . . .
I do not understand what you mean by "booster not sucking in air". ABS is acronym for antilock braking system. The ABS is fuse protected. This fuse would not have any affect on the purge valve. This fuse has no affect on the power brake booster.

Go back to post #37 and follow the detail about correct installation of the throttle position sensor. If not installed correctly this could very well be the source of your engine stall issue.
 
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