VW Jetta MKIV/MK4: 1.8t not running with full power.. |Volkswagen Bora
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  1. #1

    Default 1.8t not running with full power..

    I recently got a stage II tune with multi setting done to my mk4 03 1.8t, and when I put the car into 93 octane mode the car will sputter and then backfire with flames when I go any higher than about half throttle. When the car is in stock mode I am only getting about 50% power without any sputtering. When I have my car in stock mode and run it for about 4 hours I can usually get full power. Not too sure why this is happening, I'm not getting any check engine light or anything. I recently replaced both oxygen sensors, the car is running a 3'' catless downpipe with a muffler at the end. I put performance rated ignition coils, plugs, and a new fuel filter. Any help as to fixing this issue would be greatly appreciated..

  2. #2
    Senior Member PowerslavePA is on a distinguished road PowerslavePA's Avatar
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    Default Re: 1.8t not running with full power..

    If it was not happening before the TUNE, then, well, there in lies the trouble...

  3. #3

    Default Re: 1.8t not running with full power..

    Yeah, I originally got the tune so it would bypass my downstream oxygen sensor, and then to of course get some more power.. Do you think it could possibly be my map sensor?

  4. #4

    Default Re: 1.8t not running with full power..

    No, I think the problem lies within the tune just like Powerslave said. Who did you get your tune through?
    ~ Don't Drive Faster Than Your Guardian Angel Can Fly ~

  5. #5

    Default Re: 1.8t not running with full power..

    My bad, I misread that last post. I've had the same issue before being as it only had stock mode. The tune is just trying to make the car push harder, it was still only giving me 50% power before I had made any changes to the ECU I contacted APR and they said that their software is bulletproof, I do know that the tune has nothing to do with my power loss. I've been trying to figure out this issue for the past 8 or 9 months now slowly eliminating possibilities and getting closer to what it could be

  6. #6
    Senior Member KiDGiB is on a distinguished road KiDGiB's Avatar
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    Default Re: 1.8t not running with full power..

    Did you gap the spark plugs to .028?

    When you get tuned, you need to bring it down to .028 and we usually run the one step colder spark plug BKR7E.

  7. #7

    Default Re: 1.8t not running with full power..

    No, i didn't. I'll buy the tool to check the gapping. Even though i didn't do that, the stock gapping on the plugs shouldn't affect the stock performance should it? They're rated plugs for the 1.8t engine

  8. #8
    Senior Member KiDGiB is on a distinguished road KiDGiB's Avatar
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    Default Re: 1.8t not running with full power..

    Quote Originally Posted by Bren View Post
    No, i didn't. I'll buy the tool to check the gapping. Even though i didn't do that, the stock gapping on the plugs shouldn't affect the stock performance should it? They're rated plugs for the 1.8t engine
    What performance rated ignition coils did you install? The 2.0 coils?

  9. #9

    Default Re: 1.8t not running with full power..

    Yes, I bought them right off of ECS Tuning; but again with stock performance i'm in limp mode and I shouldn't need anything performance wise to have the car run full potential. I've talked to many people over the past months and have yet to get some sort of an idea why my car's doing what it's doing. My map sensor might have something to do with it, i'm just not sure until i put one in..

  10. #10
    Senior Member KiDGiB is on a distinguished road KiDGiB's Avatar
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    Default Re: 1.8t not running with full power..

    Quote Originally Posted by Bren View Post
    Yes, I bought them right off of ECS Tuning; but again with stock performance i'm in limp mode and I shouldn't need anything performance wise to have the car run full potential. I've talked to many people over the past months and have yet to get some sort of an idea why my car's doing what it's doing. My map sensor might have something to do with it, i'm just not sure until i put one in..
    When you upgrade to the 2.0 coils, you need to gap the plugs to .040

    Some even reported running .041 and .042 and still ran good.

    Here's a huge discussion on it if you're unsure.

    http://forums.vwvortex.com/showthrea...dom-new-stuff.

  11. #11
    Senior Member KiDGiB is on a distinguished road KiDGiB's Avatar
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    Default Re: 1.8t not running with full power..

    Here's another one that is a bit easier to read through.
    http://clubgti.com/showthread.php?25...ack-Conversion

  12. #12

    Default Re: 1.8t not running with full power..

    Sweet! Thanks, i'll look into getting a tool and checking the gaps on my plugs! I was also thinking that it could be my n75, i've never replaced it and figured it wouldn't hurt to try

  13. #13

    Default Re: 1.8t not running with full power..

    Let us know if this fixes the issue

  14. #14

    Default Re: 1.8t not running with full power..

    I gapped my plugs and haven't noticed any difference.. Still no power. I'm putting in an N75 valve tomorrow and am going to see what that does

  15. #15
    Senior Member KiDGiB is on a distinguished road KiDGiB's Avatar
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    Default Re: 1.8t not running with full power..

    You could double check that the N75 is installed correctly.


  16. #16

    Default Re: 1.8t not running with full power..

    Replaced N75 valve still nothing.. is it possible it's the map sensor or the diverter valve? I brought my car in to get looked at and a low boost code came up? What could be causing this?

    Codes:

    P0299 Turbo Under Boost (intermittent)

    Inspected all boost tubes and found no leaks

  17. #17
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    Default Re: 1.8t not running with full power..

    P0299

    I would test the DV (Push the diaphragm in and hold the vacuum nipple, if it holds in place then it's still good), Pull the TIP and check for turbo play, make a boost leak test and see if you have a boost leak, and last would be the cat is plugged.

    Did you double check the image I posted above to make sure you installed the N75 properly?

  18. #18

    Default Re: 1.8t not running with full power..

    Okay, I'll check the diverter valve and yes, I did check that I had the 75 valve installed correctly! The other thing, I don't have a car on my car, the tune is supposed to basically divert it and give the car a dummy signal

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