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Thread: B8 2.0TFSI engine stutter/hesitation/surge

  1. #1

    Default B8 2.0TFSI engine stutter/hesitation/surge

    Hi Team,

    I've been chasing a problem on my 2009 B8 A4 Quattro for some 1.5 years and have come to an end of my patience and am at a dead end. I'm hoping one of you can help me resolve this once and for all.

    The problem is I get a pretty predictable and noticeable engine hesitation/stutter/surge under the following conditions:
    • When driving under engine load, like going up a hill;
    • Constant engine revs - can be between 2k and 4k. If I accelerate the problem goes;
    • Transition from vacuum to boost - boost gauge observed at about 0 psi when it happens; and
    • The intake sounds like a kettle that can't decide if its boiling or not - I suspect the DV is opening and closing.


    From logging I've learned that:
    • The short term fuel mixture bottoms out at about -17% and is definitely below -10%;


    I've tried:
    • Upgraded DV to GFB DV+ - also replaced oem solenoid;
    • Upgraded to 034 PCV and catch can;
    • Upgraded to R8 ignition coils;
    • Replaced Spark Plugs;
    • Replaced Fuel Injectors;
    • APR Carbonio intake;
    • 034 Turbo Intake Hose; and
    • Resealed Valve Cover.


    I also tried pressure testing a few times and have not found any noticeable leaks.

    I have tried almost daily searching bing and google and have found a tonne of people with what seems like the same problem, variable valve lift seems to always get the blame. But no-one ever seems to post that the issue got fixed.

    I'm holding onto some hope that this is a fixable condition because otherwise I love the car.

    Happy to do some loggin if you suggest what to log. I'd be interested in monitoring what the ECU uses to decide the DV position but can't seem to figure out what that is.

    Thanks in advance.
    Current: 2009 B8 A4 Quattro - Racechip
    Former:
    2004 B6 A4 - APR Stage 3 (K04),
    2000 B5 A4 GP with Powerchip Gold

  2. #2
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    Default

    Is this the B6 with the APR Stage 3 K04?

    If so, what happens if you put it back to stock, compared to the 98 ron program?

  3. #3

    Default

    Thanks Jnrdavo, its a B8 2.0TFSI, I had an old signature block sorry.

    I have recently reset back to stock DV and problem still exists. I also try turning the racechip on/off. Only changes the character of the problem.

    As I said in original post, I have done these things to correct the problem. The only mod I made prior was the DV which I think we can now rule out.
    Current: 2009 B8 A4 Quattro - Racechip
    Former:
    2004 B6 A4 - APR Stage 3 (K04),
    2000 B5 A4 GP with Powerchip Gold

  4. #4

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    I'm thinking it might be a bad MAP sensor. There is a fair bit of oil in all my pipes so it's possible it's been coated over time. I logged actual vs requested charge pressure today and the actual pressure barely changed at all. It occasionally followed the requested line, but mostly stayed just below 1 bar.

    AFAIK the MAP sensor helps the engine determine fueling (and other things including boost control) so if this is failing or reading incorrectly it could result in my symptoms.

    I'll try clean the MAP with some alcohol and let you know if it made a difference.

    Any other theories out there?
    Last edited by Rebel1; February 4th, 2019 at 01:32 PM.
    Current: 2009 B8 A4 Quattro - Racechip
    Former:
    2004 B6 A4 - APR Stage 3 (K04),
    2000 B5 A4 GP with Powerchip Gold

  5. #5

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    It might be worth investigating the wastegate actuator - see here: https://motozaperformance.com/how-to...t-vag-vehicle/

  6. The Following User Says Thank You to MattA4 For This Useful Post:

    Rebel1 (February 7th, 2019)

  7. #6

    Default

    Definitely not the MAP sensor. It was wet with oil but cleaning it made no positive difference.

    Also noticed oil deposits around d the oil cap so bought a new oil cap. No difference.

    I'm rethinking it's a boost leak. Something related to a check valve, or the vacuum pump line.

    Sent from my Pixel 2 XL using Tapatalk
    Current: 2009 B8 A4 Quattro - Racechip
    Former:
    2004 B6 A4 - APR Stage 3 (K04),
    2000 B5 A4 GP with Powerchip Gold

  8. #7

    Default

    Thanks Matt,

    I reviewed the thread and thought this was worth investigating but apparently the IHI K03 utrbos on the B8 do not have an adjustable waste gate actuator.
    Current: 2009 B8 A4 Quattro - Racechip
    Former:
    2004 B6 A4 - APR Stage 3 (K04),
    2000 B5 A4 GP with Powerchip Gold

  9. #8

    Default

    Last weekend I was determined to find the fault, armed with a number of boost leak articles I set out to pressure test the car again.

    The article I used most - https://www.audizine.com/forum/showthread.php/662774-DIY-Boost-leak-testing - basically setup the test in reverse to what I had done previously so that the PCV to turbo crankcase vapour return line is blocked off and not pressurise the engine via the PCV.

    Well, after going through 3 bike tyres, the fourth one held long enough to pressure test, and again I found no leaks.

    As I put my carbonio airbox back in I put my stock Turbo Intake Pipe back in - thinking the only thing I didn't pressure test was my 034 TIP. While the OEM TIP fits much better than the 034 TIP, it sadly did not fix the issue.

    I started to investigate the EVAP system and took apart the control valve and blew threw it - it was closed as it's supposed to be.

    I also took advantage of inspecting the vacuum lines and found a couple of dodgy clamps that I replaced.

    Driving to work today the problem now seems worse. The problem now seems more prominent on the vacuum side of boost - say -3 to 0 psi according to my boost gauge. Before I thought it was in early boost.

    An evap issue makes sense to me logically, but it also has a leak test cycle which should have identified a leak if there is one. They say a 1% variance in the EVAP control valve makes a 20% difference to fueling, so the tolerances are pretty tight and would explain my -17% short term fuel trim.

    The again, so would bad spark plugs.
    I have a set of spark plugs at home that I might look into this week. I didn't check the gap on my last set so I'll test and confirm before fitting.

    Any other thoughts?
    Current: 2009 B8 A4 Quattro - Racechip
    Former:
    2004 B6 A4 - APR Stage 3 (K04),
    2000 B5 A4 GP with Powerchip Gold

  10. #9

    Default

    Not in the boost pipe system.

    Rang to book in for a Rear Main Seal replacement and the service tech suggested I check the oil dipstick plug. Well, the seal was cracked and after replacing car has been MUCH better. I had hoped it would be something simple and it was! But diagnosing is a real PITA.

    Hope this helps others.
    Current: 2009 B8 A4 Quattro - Racechip
    Former:
    2004 B6 A4 - APR Stage 3 (K04),
    2000 B5 A4 GP with Powerchip Gold

  11. #10

    Default

    Quote Originally Posted by Rebel1 View Post
    Not in the boost pipe system.

    Rang to book in for a Rear Main Seal replacement and the service tech suggested I check the oil dipstick plug. Well, the seal was cracked and after replacing car has been MUCH better. I had hoped it would be something simple and it was! But diagnosing is a real PITA.

    Hope this helps others.
    Congratulate to you. All that headaches over a little oil dipstick plug, must have driven you nut.
    2000 Avant A4 B5 Turbo Quattro - Powered by QMS E85 K04

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