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Thread: 4age erratic idle and now not running *URGENT HELP PLEASE*

  1. #1
    Junior Member Domestic Engineer MRMOPARMAN's Avatar
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    Angry 4age erratic idle and now not running *URGENT HELP PLEASE*

    hey guys, with less than a week to go till my next race meet i have encountered a huge problem, hopefully someones had before!

    the car, a KE25 with bigport JDM 4age, stock ecu and everything, aftermarket alarm.. when i go to start it from stone cold, it will run fine (eg idle high for warm up) then when it gets some warmth into it, under 2 minutes, and the idle starts to come down, it will rev to required idle, then drop off to almost a stall, then do it again and again etc etc..

    then when it gets to operating temp, after a while, it will stall. so i go to start it again and it will fire up but stall immediately, exactly like what happens with a blown ballast resistor on a points car.

    now ive actually found a diagnostic port i can check for dtcs, does anyone know how to check for codes without the proper scan tool and what they mean?

    ive checked for airleaks, couldnt find any (not much room to check btw) tried disconnecting sensors to see if it runs different in limp home mode, checked fuel supply etc.. but to no avail.

    oh btw with the erratic idle, you can hear the ECU switching off the injectors when it hits the required idle, then switches them back on when its about to stall..

    please help!

    cameron.

  2. #2
    Fuel Economy Warrior Carport Converter Vios-GT_07's Avatar
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    Default Re: 4age erratic idle and now not running *URGENT HELP PLEASE*

    idle control motor??

    if it revs fine and just can't hold idle, then yea have a look at the idle control motor.. there's a lot of stuff about it on the forums as well so have a search..

    then if it's not that, could be a spark issue so check your spark plugs, leads, distributor and ignitor.. but normally if it's a spark or fueling issue u'll have problems revving up..

    fuel is relatively simple..check your fuel filter, fuel lines and fuel pump..
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    Junior Member Domestic Engineer MRMOPARMAN's Avatar
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    Default Re: 4age erratic idle and now not running *URGENT HELP PLEASE*

    thanx for your help.. im thinking ive got 2 problems now.. the idle motor like you stated, i think is stuck open, and the computers cutting injectors to sort it out maybe?

    and although i have fuel flow, i think its way down on pressure, as i can keep the car running on aerostart. very weird problems though. normally when a pump carks it, it carks it altogether. ohwell ill get a new pump tomorrow and go from there

  4. #4
    Fuel Economy Warrior Carport Converter Vios-GT_07's Avatar
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    Default Re: 4age erratic idle and now not running *URGENT HELP PLEASE*

    oh fuel pumps mate.. i've seen the lot... on their way out they can pump a lot less fuel, causing ur engine to run lean and ping its tits off...it's actually quite rare in my book that the fuel pump stops working altogether.. just like that.. very often it's pressure that goes down, hence less volume as well.. u wouldn't even notice in the begining unless u're very enthutiastic about the engine.. but yea fuel pump deteoriation as it progresses is very noticable

    erm the idle control motor is a pulsing device.. and yea if it is stuck in one direction, u may as well not have it... hence the erratic idle..

    as for the fuel pump, i suggest you not drive your car until u sort out the fuel pump.. (VL Turbo fuel pump is a very good choice)..

    good luck mate, glad to help

    edit : no the computer isn't deliberately cutting out your injectors.. if u're revs are coming down low to a stall, there's a drop in MAP or AFM reading hence the ecu's response to it, cut fuel.. that's the right thing to do, otherwise u'd have the injectors running but not getting burnt coz no air to combust it and no spark to follow..
    Last edited by Vios-GT_07; 30-10-2006 at 04:11 AM.
    Research has shown child in front seat causes accidents, accident in back seat causes child

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    USDM tyte yo Grease Monkey Tanya's Avatar
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    Default Re: 4age erratic idle and now not running *URGENT HELP PLEASE*

    Don't forget to check the fuses, it sounds a bit lame but 8 months ago my 5M got all weird and didn't want to idle right, then it stalled and didnt want to stay running, etc, etc

    Turned out the EFI fuse was partially blown, there was still just enough there to get the car to start but it kept a horrible idle until we changed the fuse.

    Funny though, not 2 days later my fuel pump went out, lol.
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  6. #6
    Chookhouse Chooning Automotive Encyclopaedia Hen's Avatar
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    Default Re: 4age erratic idle and now not running *URGENT HELP PLEASE*

    As far as I know, a JDM RWD 4AGE doesn't use an idle motor, it uses a heated wax pellet. And it shouldn't cause any problems like what you are describing. One way to check for this is to just wind out the idle adjust screw on your throttle body (under a rubber plug) to up the idle.

    If this doesn't make it run then your problems lie elsewhere.

    Also when you say you can hear the ECU switching the injectors off when it hits correct idle, do you mean injectors or idle up VSV? Switching the injectors off is a major problem and would cause the engine to stop pretty quickly.

    I'd recommend checking fuel filters, fuel pressure and that all injectors are working properly if you suspect the fuel side of things.

    Hen

  7. #7
    Rest in Peace Conversion King ViPeR_NiPPleX's Avatar
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    Default Re: 4age erratic idle and now not running *URGENT HELP PLEASE*

    Check the main injector earth. I think it's near the fuel rail from memory. I had the same problem with a mates car from it just being either loose or bad contact.

    Extra: It's got 4 wires going to a copper ring that should be mounted to either the head or to a bolt holding down the fuel rail. The colour of the wires I believe is white with black stripe. Have a look, it only took me to tighten it up to fix it... although might not be the problem as it seems to be fine when its cold
    Last edited by ViPeR_NiPPleX; 30-10-2006 at 10:11 AM. Reason: Adding

  8. #8
    Junior Member Domestic Engineer MRMOPARMAN's Avatar
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    Default Re: 4age erratic idle and now not running *URGENT HELP PLEASE*

    thanks for all the replies guys.. last night i checked the fuel pressure.. 30psi-40psi and with the return line clamped 110psi!!

    it acutually started and ran fine last night.. couldnt belive it. adjusted the idle down via the plug (must have rattled up maybe during racing)?? and it idles well.. oh i also cleaned the idle ports in the throttle body out with CRC.

    checked the earth point on the inlet, it was tight.
    i still dont trust it though, i really havent fixed anything! ill keep running it and see if anything happens.

    thanks again! Cameron.

  9. #9
    Oberst Koi-Master Backyard Mechanic
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    Default Re: 4age erratic idle and now not running *URGENT HELP PLEASE*

    With the diagnostics port. If you can make out the terminals bridge T and E1, this will make the engine light flash.

    If it flashes constantly then there are no problems that the ECU can determine at this point.

    If there are pauses in the flashing. Count the number of flashes between each pause. You may need to watch it a few times as it will flash a code say 51 (five flashes pause one flash pause.) There is some ecu diagnostics code chart floating around here somewhere which will give u the codes and what they mean.
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  10. #10
    Junior Member Domestic Engineer MRMOPARMAN's Avatar
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    Default Re: 4age erratic idle and now not running *URGENT HELP PLEASE*

    excellent! thanks for that inertia.. my ecu doesnt have an engine light connected. you wouldnt happen to know the ecu pin/s the engine light comes out at woud you??

  11. #11
    Oberst Koi-Master Backyard Mechanic
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    Default Re: 4age erratic idle and now not running *URGENT HELP PLEASE*

    I don't for the JDM bigport. Perhaps www.club4ag.com might in their technical area.

    Or, unscrew the lid off the ecu and read off the PCB (probably most accurate way). Can't remember what the abbreviation for the checklight is, but if you look on the wiring diagrams for other 4ag's you'll find that out.
    "Welcome the dude who ain't the buyer of mugs"

  12. #12
    Junior Member 1st year Apprentice
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    Default Re: 4age erratic idle and now not running *URGENT HELP PLEASE*

    it was probably the hi-idle air bypass valve under the throttle body sticking open. they get full of grunge from people not flushing the coolant system often enough. another possible cause would be the TPS being out of adjustment and not signaling the ECU that the throttle is in the idle position,but the warms up and surges thing is almost always the air bypass valve.

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