Bad intake manifold gasket?

Posted by 775TSI, Oct 20, 2011
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  1. 775TSI

    775TSI Proven Member

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    Can a decent leak in my intake manifold gasket cause my car to run rich? My air fuel reads 18.0, so i am running lean but at cruise im around 14.5 to 15.5 which from what i read is ideal. i sprayed around my intake manifold after i replaced my injector and the idle damn near died. Also would this be my cause of boost loss? I am still hearing an obnoxious clicking when my idle drops low. Could this be my resistor pack for my injectors? I would unplug the injector that it sounded as if it was coming from 2 or 3, and it would stop till plugged back in. I am trying to knock away all possible reasons why my car is running like poo.

    Oh i am running a AEM air fuel gauge and 18 is pegged in the red to the far right. No idea how this reads lean rich or stoich since all air fuels are different on how they read, but my numbers are ------ at idle to 14.5 - 15.5 at cruise and 11 to 10 at 9 psi under pressure.
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  2. iugrad92turbo

    iugrad92turbo Proven Member

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    first i would go ahead and do a boost leak test to see if you have any leaks.
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  3. talonDSMerr

    talonDSMerr Proven Member

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    Yes, a bad intake manifold gasket will cause you to run lean at idle/cruise, and rich under load/boost. At idle, the vacuum draws in un-metered air from the leak so the air/fuel mixture goes lean. Under boost, the high pressure air inside your intake leaks out and you lose metered air, causing the air/fuel mixture to go rich.

    You pretty much pinpointed the problem when your idle nearly died as you sprayed carb cleaner around the intake manifold gasket. Fix the gasket and you're one step closer to getting your car running right.
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  4. 775TSI

    775TSI Proven Member

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    So what about the random ticking i can hear that comes and goes but is very loud at idle? It sounds like its coming from the resistor pack / Coil pack area so right in the middle of the intake manifold. I guess you could say it almost sounds like an electrical ticking, louder then a lifter tick.

    I am currently waiting to see if my CEL comes back from when it had a code for faulty circuit injector 2 (which i just replaced) and go from there. I still have not yet determined how i am getting gas in my oil hoping that the 2 injector was bad.
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  5. Colt4G63 also

    Colt4G63 also Proven Member

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    Manifold leaks can sound like ticking. Just fix the leak and see what happens.
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  6. 775TSI

    775TSI Proven Member

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    well just went and picked up my new intake manifold gasket, new valve cover gasket set, some new plugs, new throttle body gasket, and a new tool box since the wife ran mine over. Hopefully the car will run like a champ.

    Update, While moving my tools from one box to another she managed to run over my compression checker and now the glass is cracked. This just gets better and better LOL.
    Last edited: Oct 22, 2011
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  7. beendenied

    beendenied Proven Member

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    Ran over your toolbox? wow

    Get a rollaway :thumb:
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  8. iugrad92turbo

    iugrad92turbo Proven Member

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    Still you should do boost leak test to make sure.
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  9. 775TSI

    775TSI Proven Member

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    i will give an update following this post tomorrow on how everything went and how it now runs.
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  10. 775TSI

    775TSI Proven Member

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    Alright so last night did the intake manifold, Throttle body, valve cover and tube seals. Ran the car and it boosts hard but still only to 10 PSI but this time it doesn't drop and i don't get what feels like a decrease at high RPMs. The car idles very well around 900 and my Air fuel is between 14 and 15. I still do suspect more leaks and im replacing my plugs since these are majorly fouled.

    Bad news is i still hear the obnoxious ticking coming from the injector area and when that clicking starts my air fuel goes to 18+. This does it at random and for no more then about 10-15 second intervals. Really odd never heard this before on a car other then a lifter which was a constant tick.
    Last edited by a moderator: Oct 25, 2011
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  11. iugrad92turbo

    iugrad92turbo Proven Member

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    You should send him a pm if your trying to sell your items.
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  12. Funfettie

    Funfettie Proven Member

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    Boost leak test. Im not sure whats in your setup, but make sure your intake mani is the same Gen as the head.
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  13. sugarfree

    sugarfree Proven Member

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    I have the same issue with the mystery tick, curious to see if anyone actually knows what this is and why it has an effect on a/f
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  14. 775TSI

    775TSI Proven Member

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    Perfect name for it. We shall call it, the Mystery Tick! Anyone else had this issue?
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  15. Stealth93

    Stealth93 Proven Member

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    What about the injector seals? I guess a boost leak test would show that.
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  16. Funfettie

    Funfettie Proven Member

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    Mystery tick? like lifter tick? slap a set of 3g revised lifters in, and it should solve the issues!
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  17. 775TSI

    775TSI Proven Member

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    I already replaced the injector seals 2 days ago. And the tick comes on and off. Itll tick really loud for about a minute then go away for about 2-3 minutes then come back for 30 seconds then away for 10 seconds then back.
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  18. newtodsm97gst

    newtodsm97gst Proven Member

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    how did you fix your afr going lean, i'm having the same problem, mine creeps to lean like 19.5 and when i give it a gas i goes back to normal for 5 seconds then creeps to lean again. it does this on idle and while cruising with the foot on the gas.
    #18
  19. WES_393

    WES_393 DSM Wiseman

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    Lean out 0f boost could be either a vacuum leak, an exhaust leak, or a faulty O2 sensor. I would check them in that order.
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  20. 99boostedgst

    99boostedgst Proven Member

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    i have a slight constant jerk while driving anyone answer this one? and wideband peaks lean and way lean..... i have a plx wideband the square one not round style.
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  21. PFC_CiarlilloM

    PFC_CiarlilloM Proven Member

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    My manifold absolute pressure/manifold differential pressure sensor (black sensor on top of the intake manifold) randomly clicks while driving. I can even hear it at stop lights. Anyways it tested out bad (according to the Haynes manual) Might be the "ticking/clicking" you're hearing.
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  22. newtodsm97gst

    newtodsm97gst Proven Member

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    I did blt and hear something hissing by the intake manifold but I'm not sure. Crack exhaust manifold could do that also? And I have pretty new o2 sensor from innovate mtxl.
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