The Easiest Way To Find Vacuum Leak on 1.8T Passat
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  1. #1
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    The Easiest Way To Find Vacuum Leak on 1.8T Passat

    What is the best way to find out the source of the leak on 1.8T Passat?
    The car idles funny like it's going to die but drives just fine.
    Thanks!

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  3. #2
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    That sounds more like your MAF needs to be replaced.

  4. #3
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    How do I find out if MAF is bad?

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    It's not hard, just clean it out just incase..
    If it stops acting up then it was the MAF..

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    Unplug the electrical connectors to it. If the car suddenly idles better, that's probably the culprit.

    I've mentioned before, an easy way to check for vacuum leaks is to take a propane torch and crack the gas valve open a little. As the car idles, run the tip of the torch around the hoses, joins, gaskets, etc... anywhere a leak could be. If the idle suddenly surges, then you've found a leak.

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    Thanks guys, I'm going to check on the MAF later.

    here's the codes that came up:

    12 Faults Found:

    16840 - EVAP System: Very Small Leak Detected
    ***********P0456 - 001 - Upper Limit Exceeded - Intermittent

    17536 - Fuel Trim: Bank 1 (Mult): System too Lean
    ***********P1128 - 001 - Upper Limit Exceeded

    16555 - Fuel Trim: System Too Lean: Bank 1
    ***********P0171 - 001 - Upper Limit Exceeded

    17519 - Oxygen (Lambda) Sensor Regulation: Bank 1: System too Lean
    ***********P1111 - 002 - Lower Limit Exceeded

    16684 - Random/Multiple Cylinder Misfire Detected
    ***********P0300 - 001 - Upper Limit Exceeded

    16685 - Cylinder 1 Misfire Detected
    ***********P0301 - 001 - Upper Limit Exceeded

    16687 - Cylinder 3 Misfire Detected
    ***********P0303 - 001 - Upper Limit Exceeded

    16688 - Cylinder 4 Misfire Detected
    ***********P0304 - 001 - Upper Limit Exceeded - Intermittent

    16686 - Cylinder 2 Misfire Detected
    ***********P0302 - 001 - Upper Limit Exceeded

    16891 - Idle Control System RPM Higher than Expected.
    ***********P0507 - 001 - Upper Limit Exceeded - Intermittent

    17705 - Pressure Drop between Turbo and Throttle Valve (check D.V.!)
    ***********P1297 - 001 - Upper Limit Exceeded

    17544 - Fuel Trim: Bank 1 (Add): System too Lean
    ***********P1136 - 001 - Upper Limit Exceeded

  8. #7
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    Wow, that's a lot of misfires. When is the last time you changed plugs and wires?

  9. #8
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    just replaced the plugs last week and coils were done recently. I think the leak is the caused, I just don't know the easiest way to find it. Gonna check the MAF reading now.
    Last edited by windhys; 07-06-2010 at 02:04 PM.

  10. #9
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    So maf seems fine. I unplugged the wire but still idling funny. I keep getting code 17705 check DV thing everytime I cleared the codes, could that be the problem?

  11. #10
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    Look what I found





    not sure if this is the only leak spot

    now how do I take this off. Does anyone know where to look for the part number? I don't wanna take it apart until I get the replacement part.
    Last edited by windhys; 07-06-2010 at 07:36 PM.

  12. #11
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    If I am looking at that picture correctly, I believe that's a crack in your turbo inlet pipe. I had a similar crack and replaced it with one made by forge.
    http://www.ecstuning.com/Volkswagen-.../Turbo_Intake/

    As for taking it apart, follow #11-16 from this post.
    K04 Upgrade/Installation
    Last edited by denbyu; 07-06-2010 at 06:35 PM. Reason: typo #1 -> #11

  13. #12
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    Did that crack cause yours to idle funny? I'll try to take a better pic

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    I think I didn't have a problem with the idle, but that was because the crack was not as severe as yours looks. Some idle problems can be attributed to vacuum leak. But in my case, the only thing I noticed was the lack of power.

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    Looking at the codes again looks like that is the only leak spot.

    17705 - Pressure Drop between Turbo and Throttle Valve (check D.V.!)
    ***********P1297 - 001 - Upper Limit Exceeded

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    Ok so the replacement pipe didn't help. I'm still getting this code that is causing all cylinders misfired.

    17705 - Pressure Drop between Turbo and Throttle Valve (check D.V.!)
    ***********P1297 - 001 - Upper Limit Exceeded

    Any idea next part I should look into?

    Also in block 002, all last 3 readings seem higher than the limit.

  18. #17
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    You can make your own pressure tester from plumbing PVC at Home Depot or the like. I have one that I made. I also searched and see that there are at least two sites that have a how to for making one. Basically I disconnect my Air box and plug the pressure fitting into that. I don't have the time to type it all right now but you get the hint. Put an air hose on the fitting and turn the compressor up to about 25 psi. Look for any leaks. you'll find them. Unless it's electrical. Good luck.

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    Quote Originally Posted by Troy Jollimore View Post
    Unplug the electrical connectors to it. If the car suddenly idles better, that's probably the culprit.

    I've mentioned before, an easy way to check for vacuum leaks is to take a propane torch and crack the gas valve open a little. As the car idles, run the tip of the torch around the hoses, joins, gaskets, etc... anywhere a leak could be. If the idle suddenly surges, then you've found a leak.
    of course, the flame must be off. you're only using the gas.

    Quote Originally Posted by noodles View Post
    Wow, that's a lot of misfires. When is the last time you changed plugs and wires?
    those misfires are unrelated to plugs and wires... they're the symptom of whatever is happening...

  20. #19
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    There is weird noise everytime I shift to reverse or drive, It sounds like when you just open drivers door

    Here's the link to the sound clip.
    http://www.youtube.com/watch?v=AQ2CVvhaass

    LOL

  21. #20
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    Have you checked the diverter valve? If it's leaking (passing air) you won't catch that with a boost leak tester.

    The noise in the video could be a number of things. One of those things it might be is air passing through a hole/cut/split in a hose and making a humming noise. A ruptured Diverter Valve diaphragm may also hum, but I don't know if you'd get that at idle.

    Best advice so far was the suggestion to make a boost leak tester and see what shows up.

    As for the propane trick, that's something I used to use all the time on older engines. On these newer computer controlled and idle stabilized engine systems, it doesn't work as well. The engine has to be running super lean beyond the ECM's ability to compensate before you see any change in idle. If it isn't that far out of whack, the computer will compensate and when the propane is added, the computer stops compensating. You may not detect any change in idle because the system responds so quickly. So in other words, if the propane trick fails to pinpoint a leak, that does not mean you still don't have a leak. It just means the ECM can compensate for the leak faster than the propane trick can point it out.

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    Quote Originally Posted by Steve in Chicago View Post
    Have you checked the diverter valve? If it's leaking (passing air) you won't catch that with a boost leak tester.

    The noise in the video could be a number of things. One of those things it might be is air passing through a hole/cut/split in a hose and making a humming noise. A ruptured Diverter Valve diaphragm may also hum, but I don't know if you'd get that at idle.

    Best advice so far was the suggestion to make a boost leak tester and see what shows up.

    As for the propane trick, that's something I used to use all the time on older engines. On these newer computer controlled and idle stabilized engine systems, it doesn't work as well. The engine has to be running super lean beyond the ECM's ability to compensate before you see any change in idle. If it isn't that far out of whack, the computer will compensate and when the propane is added, the computer stops compensating. You may not detect any change in idle because the system responds so quickly. So in other words, if the propane trick fails to pinpoint a leak, that does not mean you still don't have a leak. It just means the ECM can compensate for the leak faster than the propane trick can point it out.
    No humming when idle. It sounds like when you just unlock and open driver's side door. How do you find out if the dv is bad?

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    Quote Originally Posted by windhys View Post
    No humming when idle. It sounds like when you just unlock and open driver's side door. How do you find out if the dv is bad?
    I had the same issue, and it turned out to be a bad DV. I have had several of the other codes you mentioned, I will take a closer look at them and let you know what I did to fix.

  24. #23
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    Quote Originally Posted by windhys View Post
    How do you find out if the dv is bad?
    Pull the valve off the car and see if it holds pressure when you try to blow through it. You should be able to blow hard into either of the large ports with NO air passing through the valve.

    Stick your little finger up the bottom port and push the plunger up off the seat, then close off the small vacuum port with another finger, then release the finger pushing the plunger. The plunger should stay off the seat (valve open) until you release the vacuum.

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    Quote Originally Posted by windhys View Post
    Thanks guys, I'm going to check on the MAF later.

    here's the codes that came up:

    12 Faults Found:

    16840 - EVAP System: Very Small Leak Detected
    ***********P0456 - 001 - Upper Limit Exceeded - Intermittent

    17536 - Fuel Trim: Bank 1 (Mult): System too Lean
    ***********P1128 - 001 - Upper Limit Exceeded

    16555 - Fuel Trim: System Too Lean: Bank 1
    ***********P0171 - 001 - Upper Limit Exceeded

    17519 - Oxygen (Lambda) Sensor Regulation: Bank 1: System too Lean
    ***********P1111 - 002 - Lower Limit Exceeded

    16684 - Random/Multiple Cylinder Misfire Detected
    ***********P0300 - 001 - Upper Limit Exceeded

    16685 - Cylinder 1 Misfire Detected
    ***********P0301 - 001 - Upper Limit Exceeded

    16687 - Cylinder 3 Misfire Detected
    ***********P0303 - 001 - Upper Limit Exceeded

    16688 - Cylinder 4 Misfire Detected
    ***********P0304 - 001 - Upper Limit Exceeded - Intermittent

    16686 - Cylinder 2 Misfire Detected
    ***********P0302 - 001 - Upper Limit Exceeded

    16891 - Idle Control System RPM Higher than Expected.
    ***********P0507 - 001 - Upper Limit Exceeded - Intermittent

    17705 - Pressure Drop between Turbo and Throttle Valve (check D.V.!)
    ***********P1297 - 001 - Upper Limit Exceeded

    17544 - Fuel Trim: Bank 1 (Add): System too Lean
    ***********P1136 - 001 - Upper Limit Exceeded
    I had 16840, replacing the gas tank cap fixed it.

    17536/16555 came up because my MAF was dirty. I went and bought some CRC electronics cleaner and cleaned it. Slipped it back in and went away. However, now my MAF is having issues again, so I am replacing it. Found it for under $60 on eBay.

  26. #25
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    Quote Originally Posted by pootergeek40 View Post
    I had 16840, replacing the gas tank cap fixed it.

    17536/16555 came up because my MAF was dirty. I went and bought some CRC electronics cleaner and cleaned it. Slipped it back in and went away. However, now my MAF is having issues again, so I am replacing it. Found it for under $60 on eBay.
    I tried unplugging the MAF while engine was still running, didn't change the idle.

  27. #26
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    Quote Originally Posted by Steve in Chicago View Post
    Pull the valve off the car and see if it holds pressure when you try to blow through it. You should be able to blow hard into either of the large ports with NO air passing through the valve.

    Stick your little finger up the bottom port and push the plunger up off the seat, then close off the small vacuum port with another finger, then release the finger pushing the plunger. The plunger should stay off the seat (valve open) until you release the vacuum.
    I'll check the dv tomorrow morning

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    oh, may want to also check the side mount intercooler... sometimes they can come apart from age.

  29. #28
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    of course, the flame must be off. you're only using the gas.
    That's why I didn't say to light the torch, sipes. But then you never can count on people to follow directions properly.

    Light the propane torch and hold it up next to your rubber hoses. Bingo! You've found a leak! *Laugh*

  30. #29
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    Looks like I'm building a smoke machine. Just checked the DV and it's fine
    any idea other place to look for leak? Oh there is hissing somewhere around oil dip stick. Anything I should look there?

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    Torch didn't help

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