Ep2 overboost/fuel cut/lean afr

Discussion in 'Forced Induction (All Gens)' started by Shuggy1, Jan 11, 2017.



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  1. Shuggy1

    Shuggy1 New Member

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    Over the last week my civic has developed a ton of problems,firstly alternator stopped charging turned out to be a broken signal wire,the car is set to 14psi boost but was boosting to 20psi up until yesterday where it now hits a solid fuel cut at 10psi.the afr at idle is --- on an aem wideband if i rev the car it will return to normal 14.1-13.8 for a few seconds and lean out and idle rough.the car is running a kpro ecu,anyone any ideas as to whats happening?
     
  2. MotorMo

    MotorMo Respected

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    Maby over boosting it caused more boost leaks, that now have turned into vacuum leaks at idle. Recommend going back to your tuner.
     
  3. Shuggy1

    Shuggy1 New Member

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    What would cause the overboost in the first place?and why would it be cutting fuel at 4 psi under normal boost
     
  4. MotorMo

    MotorMo Respected

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    What is your current set up (specs)? Is your tune running on open, or closed loop? If closed loop, is it reading off of a factory air/fuel sensor, or an aftermarket wide band air/fuel sensor?
    You could always try to reflash with Kpro- maby the alternator signal wire failure caused something to get tweeked in the map/tune.
     
    XpL0d3r likes this.
  5. Shuggy1

    Shuggy1 New Member

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    Not 100% but its running an aem wideband sensor after the cat,once the wire was repaired the car ran spot on,drove home parked it up started it the next day and the afr was all over the place,repaired vaccuum pipe from turbo to wastegate today that was split so hopefully thats the overboost sorted but still got the weird afrs goin on
     
  6. MotorMo

    MotorMo Respected

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    Sounds like your on the right track, checking the basics like vacuum hoses.
    If you have a wide band air/fuel sensor reading after the cat, and your cat isn't hollowed out, its going to give false air/fuel readings. To properly read what and how your engine is burning, the sensor needs to be before the cat. The pre-cat sensor and a post-cat sensor on modern cars have two different and separate functions. The post-cat sensor is only there to tell the computer that the cat is working- it has no relation to the air/fuel trim. Verses the pre-cat sensor that tells the ECU how to "fine tune" the fuel trim by reading the left over fuel coming out the exhaust manifold. That would explain why the sensor is reading so lean- if your cat is working it should show a lean situation after the cat, since the cat turns exhaust fumes into CO2 and H2O. Also when you rev the car, it pushes more fuel down the piping so you should see an increase of your A/F ratio until the cat catches up to the increased fumes,
    A trick is to get a "bung" welded in before your cat, probably close to your other primary O2 sensor at the collector. The important thing is that the sensor bung is on the upper half of the collector- other wise if its too horizontal, it can get moisture and such in it.
     
  7. Shuggy1

    Shuggy1 New Member

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    Should have been a bit more clear,the "cat" isnt actually there its just a straight pipe from turbo to backbox,the wideband is just after where the cat should be and is the bosch wideband sensor,the pre "cat" sensor is just a factory style sensor that you can just see behind the wastegate in the picture
     

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  8. XpL0d3r

    XpL0d3r What Civic? Staff Member Registered VIP Registered OG 5+ Year Member

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    I had a similar issue that I chased around for months. It drove me absolutely bonkers, even my tuner wasn't sure of the issue.
    It turned out to be a faulty MAP sensor.
     
  9. Shuggy1

    Shuggy1 New Member

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    how did you find this out?i literally drove my car for a night went home let it cool,went out next day and everything went wrong at once
     
  10. XpL0d3r

    XpL0d3r What Civic? Staff Member Registered VIP Registered OG 5+ Year Member

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    The tuner ended up finding it when testing with a multimeter, whatever voltage it was supposed to see at idle was inconsistent. It turns out that it was a knockoff Chinese MAP sensor, but was sold on eBay as a real Omni one. I contacted the seller and ended up getting a refund.

    http://www.hrtuning.com/forum/viewtopic.php?t=1434

    (I said it was a Hondata sensor in the post above, but that's wrong lol)
     
  11. MotorMo

    MotorMo Respected

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    Just out of curiosity, what size is your exhaust plumbing. Clean looking set up by the way :thumbup:
     


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