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Thread: Seems my car has developed a fault..

  1. #1
    Join Date
    Apr 2012
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    Default Seems my car has developed a fault..

    Vaux Astra 1.6 1999

    Where do i start ?

    Alternator went a few weeeks ago so i replaced this,
    all seemed well then the idle started being erratic dropping from 500 rpm up to 1500 rpm

    i have been told its many things i have cleaned throttle body out replaced ICV checked for air leaks no fault codes or eml showing.

    i have disconnected the egr and this dos not make any difference just throws on the eml ........

    could it be the Alt ?

    14.5 v shown when running

    drops when steering wheel is turned to about 12.3v
    Last edited by badawn; 05-04-12 at 14:39.

  2. #2
    Join Date
    May 2008
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    8,449

    Default

    The absolute minimum must be 12.6v or the battery is not charging. With the engine running, switch the headlights, heated screen, heater blower etc on. Take the charging reading. If it is below 13.8v then the alternator is faulty.

  3. #3
    Join Date
    Apr 2012
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    Ok the weirdist thing just happened i turned on the AC and the revs jump up to 1500 rpm and sit there ?

    idle drops when i turn on the blower and judders

    will do a test on the input voltage tomorrow am with everythin on

    i have been told it could be that the new alt and battery spiked the Ecu is this possible and would it not run at all if this was the case ?

    thanks for the help so far

  4. #4
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    May 2008
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    Obviously the aircon and power steering are driven by the same belt so connected. When you use the power steering or switch on the aircon, this produces a drag on the engine and the revs drop.. The ECU compensates for this and raises the revs to maintain the correct idle speed. So it may be that the alternator has developed an internal fault in its regulator. Check the charging rate as above and if it does not meet the minimum then suspect it.

  5. #5
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    Apr 2012
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    ok i did test on battery and alt this am with load and with out load


    idle with no load rpm 900 14.8 v
    idle with lights on rpm jumps to 1000rpm 14.7 v
    idle with air con, heated screen lights fan all going idle jumps up to 1600rpm and sits there 14.4v

    but my tester tell me charge battery even though it shows 14.4 v ?

    its driving me nuts now

    is it the alt or now the battery thats suspect

    battery when not running shows 13.8 v then when load tested drops to 10.5v shows pass and weak ?

  6. #6
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    May 2008
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    After the load test and drop to 10.5v did you watch the battery recover? On its own with everything off it should recover around 0.1v per second or two all the way back up to a min of 12.6v.

  7. #7
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    Apr 2012
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    yeah it recovers back to normal after every think has been turned off revs drop to normal but still hunt up and down about 200 to 300 rpm below the 900 ish mark

    nothin obvious to me if the alternator is faulty is it worth replacing with a high amp alternator rather than the 70amp a certain european car parts place said is fine for the job with maybe the 100amp or 120 amp ?

    the car starts first time every time no loss of power from the battery from the look of it..

  8. #8
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    May 2008
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    I think you have eliminated all that you can now. I'd recommend a proper and thorough diagnostic check. The EGR valve disconnection proves nothing. You need to see the feedback voltage on a diagnostic tool to see what the voltage is to eliminate it. Have you checked all the vacuum pipes for leaks? Have you removed the rocker cover to sump breather pipe and checked inside for gunk and blockage? These you can do without special tools or equipment.

  9. #9
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    Apr 2012
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    ok will have a look at the breather hose on the rocker cover is that the one with the wire mesh filter in the rocker cover ? i have a proper a good diagnostic tool just havent figured out how to use it properly yet lol

    i think i will replace all the vacuum pipes just as a precaution as pin holes are hard to see i guess.

    yeah but when i disconnected the EGR valve it threw on the EML would it not do that if it was faulty in the first place ?

    thanks for the help so far

  10. #10
    Join Date
    Oct 2011
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    you need to reconnect the egr and remove the fault code then go from there to having all the codes read as some do not show up on some diagnostic readers..

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