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Not the alternator, sure seems like it though

Discussion in 'ECU's, Electronics, and Tuning' started by Periculum, Oct 21, 2010.

  1. Periculum

    Periculum Senior Member

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    So the problem is back. I thought I had fixed the issue, I tightened down a few loose electrical connections and check for grounded wires, to no avail. The car did run fine for about 300 miles before showing off the problem again. My 87Si has been acting like the alternator is dying. At low RPMs the voltage light comes on. This problem also seems to be causing the engine speed to jump up and down, much like a vacuum leak would cause. It's not the alternator, it was tested and tested fine. I also tried a new alternator and the car did the same exact thing. The battery has been replaced since this issue began and I also changed the battery terminals just in case. None of these things provided a change. If you need to know anything else, just ask.
     
  2. Briansol

    Briansol Admins Admin VIP

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    could be a bad engine ground. go around and check them all. you might want to add a few as well (just use some 8-ga amp power wire/etc)
     
  3. 8secHonda

    8secHonda New Member

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    if im not mistaken there is a sensor that will cause that light to come on but im lost for thought on what it was..
     
  4. 78civic

    78civic Junior Member

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    Did you check:
    1- the 3 or 4 main fuses up by the shock tower? (I've seen everything from coat-hangers to 115v electrical cord in there)
    2- Those goofy + cables with the little fuse in them. They soak in acid in the windings of the cable and you don't see it under the plastic skin. It doesn't cost much to run new cables..
    If it's bad I might have one or two.
    3- Check the ecu under the seat. Is it all corroded...? Showing any codes?
    4- I'm sure you DIDN"T take it to autozone to have some flunky dig around for the "right" connector, and was texting his boyfriend while he was supposed to check it "under load"..?
    5- Is it HOT to the touch at startup idle? If the alt is good and battery is bad or going (low on water/acid) the alt has to work double-time to charge up the battery. OR the rectifier/regulator went bad and it's running wide open.
    6- engine speed or tach jumping? If it's revving up a few hundred r's, then it might be the IAC valve. Since its' gotten cooler out the wax in there takes longer to warm up and let the valve flow/suck.

    E
     
    Last edited: Oct 21, 2010
  5. Periculum

    Periculum Senior Member

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    I rebuilt the engine ground coming from the valve cover. I don't really know where more are. I'll happily check those if someone wouldn't mind telling me where the others are.

    Unfortunately, it's not just the light. It will (because it has before) cause the car to eventually stop running.

    I have checked the fuses, no problems there.
    I changed the terminals, but didn't realize the wire could get so bad inside that they might stop working. I'll look into that. I'm pretty sure the sets I saw at autozone were only around 12 bucks.
    The ECU has a corrosion spot on the top, but doesn't look like anything should be affected inside.
    I have a good friend at autozone that makes sure things are taken care of properly for me. I don't trust just anyone there.
    The battery should be good, as it's relatively new, but I'll give it another check.
    The tach would jump just a hair while it runs. I figured it was just a fluke because it didn't seem to affect the behavior of the car at all. The rpms will jump a few hundred during startup. Before it used to be the coolant system not being fully bled. I can check the IAC valve. I had to check and clean it on my 91. Would that have an effect on the voltage at all?



    Thanks for all the responses guys. Last time I asked this question, I got little response. I got back and was overwhelmed at the detailed responses. Thanks!
     
  6. steady14s

    steady14s New Member

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    i have a 88 civic with a b18a swap and my lights are looping ,my heat and gas gauge are acting up .just changed out alt today with brand new one. read 14.3 v at first but is now doing same shit minutes later and reading 11 to 9v and less.....wth! any help
     
  7. friendayaz

    friendayaz New Member

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    hmm... is this a rebuilt/swap...., Or is it on its original wiring??
     
  8. friendayaz

    friendayaz New Member

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    if you are using original wiring then the symptoms are that of a faulty sensor readings.
     
  9. josh_crewdson@y

    josh_crewdson@y New Member

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    check the eld inside the fuse box. electrical load detector.
     
  10. RHDism

    RHDism Right Hand Drive guru

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    X2 :thumbsup:
     
  11. friendayaz

    friendayaz New Member

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    Check the IAC valve also.

    The IACV can cause any of the following (mostly related to idle problem)

    High RPM even after a long drive.
    Abrupt Changes in RPM
    RPM going very low on Idle up.
    etc etc

    All these are caused as the IACV gets clogged up with carbon remains or dust particles. But you can clean them up easily with Clean petrol or WD40. Here's the link to help you understand it better.
    Cleaning IACV (Idle Air Control Valve) - PakWheels Forums
     
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