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Engine Trouble.. O2 Sensor?

Discussion in '4th Generation Honda Civic (1988-1991)' started by Rich F, Sep 5, 2017.



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  1. Rich F

    Rich F New Member

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    I have a long standing problem that is getting worse. The engine runs poor under the following conditions-end of cold start to full temp engine has poor power between 1500 and 2500 rpms. worst at 1750. It suddenly will run proper as the rpms get close to 2500. On cold start their is no problem-fully heated mild problem-in between it's bad. No codes- The problem is much worse if their is a bubble in the cooling system.
    I have for one reason or another replaced the following with no effect to this problem
    fuel injectors
    fuel pump
    engine coolant temperature sensor
    exhaust sensor
    brain
    It seems like I am running lean or mistimed during the 1500 to 2500 range and when the temp is intermediate it runs badly, may misfire, ect.
     
  2. boofoo

    boofoo Respected Registered VIP

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    How often is there an air bubble in the cooling system?

    If you unplug the O2 sensor, does the engine run much better?

    Have you replaced the fuel filter and tested the FPR?

    Post a pic of the ECT sensor you replaced.
     
  3. Rich F

    Rich F New Member

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    I have replaced both the fan switch and the transducer-just recently I replaced the transducer again that is the temp sensor by the distributor. The water leak is due to a pump/block problem that has not been fully stopable after 3 waterpumps now-I run on stop leak and peiodic refills. The bubble problem has an accumlative effect-run long with a bubble and it gets worse and worse each time I run with a bubble. I'll see if I can't try running with out the O2 when I can get to the car.
     
  4. boofoo

    boofoo Respected Registered VIP

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    ^Answer?

    Have you tested for blown head gasket?

    Have you pressure tested the cooling system in an attempt to locate the coolant leak?
     
  5. Rich F

    Rich F New Member

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    I have not replaced the fuel filter-I can tell that that is not at issue-I can run 2500 to red line just fine, if the filter was clogged the motor would starve more and more as rpm's and load increases instead it improves at 2500 rpms suddenly!! The problem stops, and it runs perfectly from 2500rpms to redline.
     
  6. boofoo

    boofoo Respected Registered VIP

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    Doesn't rule out the FPR.
     
  7. Rich F

    Rich F New Member

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    I have replaced my O2 sensor twice now and the first time I used a generic sensor-only improved a bit. The second one was an aftermarket and the improvement was much more-- but still I have some problems at 1500 to 2000 rpms. I noted that the Honda O2 sensor from Honda is $200.00 -maybe they know aftermarket is substandard. Have others found the O2 sensor to be hit and miss on aftermarket? Any aftermarket O2 sensor line known to be adequate?
     
  8. boofoo

    boofoo Respected Registered VIP

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    What makes you conclude that the "problem" has anything to do with the O2 sensor?

    What exactly is the "problem"?
     
  9. Rich F

    Rich F New Member

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    My 1991 civic lx runs poorly between 1500 and 2000 rpms-It runs lean . Cold start it runs perfect but in a minute or two it runs poor between 1500 and 2500rpms.
    I replaced the original O2 sensor and it improved some. The problem became worse over time and on your recommendation I unplugged the O2 sensor and it ran much better. I bought a new sensor and it runs only slightly better than running with no sensor.
    In the past you and I have been over things like fuel filter, pressure regulator and O2 sensor--- and disconnecting the O2 sensor made a major improvement but I'm still not back to as good as it should be.
    It is very clear that the problem is the fuel mix--- and that it is only 1500 to 2500 that it happens-runs perfect cold--best it runs is on cold start but in a very short time the cold start setting ends and it has low power and misfires some in that 1500 to 2000 range.
    I have replaced the ecu- not it! I replaced the water temp sensor- the one at the distributor end of the motor-not it. I replaced the fuel injectors-not it! I replaced the fuel pump-not it!
    I replaced the O2 sensor with a cheap ($5) generic o2 sensor and modest improvement!!!! I replaced the O2 sensor with a modest priced ($7)aftermarket O2 sensor and much better but still not good enough. I looked up the Honda part from Honda and $200.00-Dam!
     
  10. boofoo

    boofoo Respected Registered VIP

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    For testing purposes, how does the engine run if you unplug the O2 sensor?

    If it's not perfect, then there is a separate problem.

    What codes are thrown?

    Why did you create a new thread if this is the same problem?
     
  11. Rich F

    Rich F New Member

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    Running without the O2 sensor the car runs a little worse than with the new sensor. So then there is an other problem yet to solve.
    The only code is when I run without the O2 sensor-codes for O2 sensor. The only things left I can guess is the intake temp-the MAP, the crank angle/crank speed.
     
  12. boofoo

    boofoo Respected Registered VIP

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    There's a non-O2 sensor problem. Fixing it will likely solve your problem.

    Check the ignition timing, measure the fuel pressure, and test the FPR. Then go from there.
     
  13. Rich F

    Rich F New Member

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    The timing is good-I do not know how to test the FPR-also my manual only gives a volumetric test for the fuel pump. Were would I tie in to do a fuel pressure test?

    For arguments sake if the FPR and fuel pressure are good were would I go next?
     


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