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Thread: 1.8T Engine Problems... Engine Guru Neurons in Dire Need!

  1. #1
    New Member VeeDubMan has a spectacular aura about VeeDubMan has a spectacular aura about VeeDubMan's Avatar
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    1.8T Engine Problems... Engine Guru Neurons in Dire Need!

    Good day everyone,

    I’m looking for technical expertise, not guesses, to help me cost-effectively troubleshoot a problem with my 2001 Jetta 1.8T engine.

    Engine
    2001 Jetta 1.8T 150HP AWW

    VAG-COM Retrieved Error Codes:
    17705 - Pressure Drop between Turbo and Throttle Valve (check D.V.!)
    16684 - Random/Multiple Cylinder Misfire Detected (across all 4 cylinders)

    Symptoms:
    Car run rough when started, especially on cold days, and stalls
    Car runs fine while moving but when it comes to a stop, the RPM drops and often stalls
    Runs great on the highway with absolutely no loss of power
    Seems to get great mileage on the highway (drove 4 hours yesterday)
    Oil accumulating on lower hose under manifold on the T-joint

    Already Tried:
    1) Changed all spark plugs and checked gaps
    2) Changed air filter
    3) Changed DV
    4) Cleaned throttle body
    5) Cleaned MAF
    6) Changed upper oil breather hose, which was cracked bad
    7) Added fuel injector cleaner and went through a full tank of gas in a 4 hour drive
    8) Looked everywhere for a hose leak/crack but came up empty

    MAF VAG-COM Results (RPM on left versus Air Mass in g/s on right)

    Run #1
    760 9.42
    1240 6.69
    1520 8.06
    1720 8.36
    1720 23.03
    1600 13.47
    2160 38.89
    3080 54.89
    4040 73.17
    5040 90.83
    5840 100.61
    6480 101.33
    4640 81.83
    4920 84.11
    5240 92.36
    5560 95.78
    5800 98.17
    6080 98.69
    6280 99.39

    Run #2
    2040 5.22
    3720 37.19
    3560 21.31
    4320 78.14
    5280 94.42
    6040 102.19
    6280 24.36
    4680 80.83
    5040 89.22
    5360 93.22
    5640 96.61
    5920 97.5
    6160 98.36
    6360 100.39

    So, is there anyone out there that had similar problems and could help me fix these issues? I do not just want to randomly spend hundreds of dollars changing parts (MAF, coil packs, hoses, coil pack harnesses, etc) but need an action plan. I thought that the MAF may be bad as it seems to read low but if there is a vacuum leak after the MAF, that would explain why it is measuring less air passing through it. If I changed the coil packs, this should not fix the vacuum leak, which I tried to find to no avail.

    I would greatly appreciate any help since I am low on cash to bring it to the stealership.
    2001 Jetta 1.8T Wolfsburg Edition

  2. #2
    Veteran Member Punjabi_Dubber has a reputation beyond repute Punjabi_Dubber has a reputation beyond repute Punjabi_Dubber has a reputation beyond repute Punjabi_Dubber has a reputation beyond repute Punjabi_Dubber has a reputation beyond repute Punjabi_Dubber has a reputation beyond repute Punjabi_Dubber has a reputation beyond repute Punjabi_Dubber has a reputation beyond repute Punjabi_Dubber has a reputation beyond repute Punjabi_Dubber has a reputation beyond repute Punjabi_Dubber has a reputation beyond repute Punjabi_Dubber's Avatar
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    Coilpacks for the misfire?
    bankrupt.
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  3. #3
    Veteran Member CaptainSlow is a name known to all CaptainSlow is a name known to all CaptainSlow is a name known to all CaptainSlow is a name known to all CaptainSlow is a name known to all CaptainSlow is a name known to all CaptainSlow's Avatar
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    Quote Originally Posted by Punjabi_Dubber View Post
    Coilpacks for the misfire?
    Most likely the misfire code was thrown because of the rough cold start idle.

    MAF numbers look fine (seems like your car is bone stock)

    Have you pressure tested the turbo system?

    Its cheap and easy.


    ALSO:

    Check the PCV hoses/check valves coming from oil filter housing.


    Try starting the car with the MAF sensor unplugged. See if it starts better when cold?

    If it does, thats your problem. I've had that issue before.

    Also, Seems like its a boost leak because of the pressure drop between turbo and throttle valve.


    Good luck and good post on the symptoms. Hope the problem is an easy fix.
    B6 A4 1.8TQ - DD

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    Veteran Member awya14 has a spectacular aura about awya14 has a spectacular aura about awya14's Avatar
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    sounds so familar..I will have to check my codes from a post a few months ago..but most likely coils ..I know thats my answer for everything now..but I took mine to my local shop 8 times to get scanned(free) and spent an hour at the VW dealership in Belleville $90 with all 4 there best engine experts and they couldnt figure it out ..the only guy who was right in the end was the guy that called the coils ..worked fine for a week ..then acted up..missfires ..thottle body codes ..I almost replced my whole throttle body ..I must have pulled my MAF out and cleaned it 20 times ..change my DV ..in the end coils..and plugs (just to be safe)..10,000+km now and everything has worked perfect ..as I mentioned in tonebags thread I had 1 coil pop up on me several times ..so I bought the bolt ons..
    2001 wolfsburg

  5. #5
    Veteran Member awya14 has a spectacular aura about awya14 has a spectacular aura about awya14's Avatar
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    these were my codes..I didnt add my missfire codes ..but they were the same too ..almost looks like the same thing ..another thing to check too is your turbo inlet hose mine was torn were the DV goes in ..just a thought

    Trouble codes

    17579/P1171/004465 - Angle Sensor 2 for Throttle Actuator (G188) Implausible Signal

    Possible Symptoms
    • Malfunction Indicator Lamp (MIL) active
    Possible Causes
    • Angle Sensors 1/2 for Throttle Actuator (G187/G188) faulty
    • Power Supply for Angle Sensors 1/2 for Throttle Actuator (G187/G188) faulty
    • Wiring/Connector(s) from/to Angle Sensors 1/2 for Throttle Actuator (G187/G188) faulty
    Possible Solutions
    • Check Angle Sensors 1/2 for Throttle Actuator (G187/G188)
      • See Measuring Value Blocks (MVB), usually MVB 062
    • Power Supply for Angle Sensors 1/2 for Throttle Actuator (G187/G188) faulty
    • Wiring/Connector(s) from/to Angle Sensors 1/2 for Throttle Actuator (G187/G188) faulty
    17705/P1297/004759 - Pressure Drop between Turbo and Throttle Valve (check D.V.!)

    Possible Symptoms
    • Power Loss
    Possible Causes
    • Leaking hoses and/or pipes between components
    • Check Boost Pressure Control Valve (N249)
    Possible Solutions
    • Check hoses and/or pipes between components
    • Check / Replace Boost Pressure Control Valve (N249)
    • Check / clean Throttle Valve, do Throttle Body Alignment
    Special Notes
    • Did anyone fitted an extra (wrong) dump valve?
    17972/P1564/005476 - Throttle Actuator (J338): Under-Voltage during Basic Setting

    Possible Symptoms
    Possible Causes
    • Battery Voltage too Low
    Possible Solutions
    16514/P0130/000304 - Oxygen (Lambda) Sensor B1 S1: Malfunction in Circuit

    Possible Causes
    • Oxygen (Lambda) Sensor Heating Bank 1 Sensor 1 faulty
    Possible Solutions
    • Check Oxygen (Lambda) Sensor Heating Bank 1 Sensor 1
    And the random missfire codes ..but they were a result of the MAF drama
    2001 wolfsburg

  6. #6
    New Member VeeDubMan has a spectacular aura about VeeDubMan has a spectacular aura about VeeDubMan's Avatar
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    Unhappy

    Quote Originally Posted by CaptainSlow View Post
    Have you pressure tested the turbo system?

    Its cheap and easy.
    I agree but I do not have access to a compressor to perform the pressure tests that people have successfully tried in the past... I am also not clear exactly where to apply the pressure through which exact hose.
    2001 Jetta 1.8T Wolfsburg Edition

  7. #7
    For the pressure drop check all the rubber hoses running from your dv down to the engine.. You'll definitely have a leak somewhere.

    also check your turbo inlet pipe like mentioned above [runs from maf housing down to turbo] factory ones are garbage.

    Missfires will be coilpacks or maf taking a dump.

    pressure test: the airbox is connected to the maf and thats connected to your turbo inlet pipe. What you do is unhook the maf and plug in a homebrew pressure tester to the inlet pipe and load the system no higher then 18 psi with air.. you'll hear the pipe hissing with air and hopefully somewhere else you will hear the same hiss as its escaping your broken hose.

  8. #8
    Veteran Member Prowler911 is a jewel in the rough Prowler911 is a jewel in the rough Prowler911 is a jewel in the rough Prowler911's Avatar
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    Hey man, all the suggestions above are valid points, but i have a feeling that is none of the above.

    I've been working on trying to "fix" this issue for 3 years. (since i switched to standalone). The symptoms you describe are 100% identical to what I was seeing. One other symptom I was seeing is HIGH idle (1000-1100rpm) after a lot of spirited driving and beating on the car, on very hot days.

    The problem resides in your TB Motor. When car is cold and idling the motor is supposed to open fully to allow more air to go by the throttle plate to keep the motor running.
    In my case, when i switched to standalone, i lost the control of this motor (because standalone was not advanced enough to control it). After going back and forth with the guys from 034 Motorsports, they released a new software version and ability to wire extra output to the motor and control it.
    Since I've done this mod and spend a lot of mornings tuning the amount it opens, I've been able to "fix" the problem.

    In your case something is probably out of aliment or faulty.These new TBs don't have mechanical adjustment via Screw for idle control. You can however open up the TB, find where the dead stop is and move that, which moves the point where the motor stops when cycling.
    However I would start by simply trying to do the TB alignment via Vag Com and let the car re-learn the 0% and 100% TB open and the Start and Stop points for the motor.
    It could be simply that the ECU's parameters don't match the TBs.
    Next I would try to swap a new TB on there (and obviously calibrate the ECU for that).

    For a short term solution, do the following:
    - When you start the car, apply lite throttle (if you apply too much car will immediately stall), raise the RPMs to about 2000-2500 and hold for 1 minutes.
    Slowly let the RPM come down to idle.
    Start driving with lite throttle input. When you come to a stop, don't the the RPM bounce down..it will stall, instead, downshift and let the the rpms come down slowly under load, put in neutral just before you reach 1000rpm. Stop.
    Repeat until Engine reaches full operating temps, when the idle motor is no longer being used.

    As an encouragement point, this happens a lot more and its alot worse in winter, fall and spring and its not so bad during summer months.

    Hope this helps.
    Last edited by Prowler911; 03-07-2010 at 02:54 PM.
    Nick | 2001 Golf 1.8T | www.mygolfiv.com | www.gtan.ca | HID Kits | Mechanic Gloves | Need Hosting ? $6/Month IM Me |

  9. #9
    Veteran Member awya14 has a spectacular aura about awya14 has a spectacular aura about awya14's Avatar
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    thats my problem too ..or was ..TB nonsense ..almost replaced it , luckly it sorted out after replacing the coils and plugs^^^^^ good write up
    2001 wolfsburg

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