Digifant Idle at 2.5-3k When Warm

Discussion in 'Engines' started by nickh89GTi, Jul 3, 2008.

  1. nickh89GTi Forum Member

    Joined:
    May 10, 2008
    Likes Received:
    0
    Location:
    Exmouth
    Hi guys.

    Finally had some time yesterday to have a little play with my 89 GTi with digifant ecu.

    The problem i have is that when started from cold it idles about 950, but once been out for a drive and it has warmed up when you turn it off and on again the it idles itself up to 2.5-3k. Let it cool down then tried again and the idle was fine at about 950. [:s]

    Can anyone shed some light as to what may be causing the engine to run like this? Any help much appreciated peeps.

    Cheers Nick
     
  2. moretorque Forum Member

    Joined:
    Aug 26, 2007
    Likes Received:
    0
    Location:
    Reading
    you have to much air getting into the system somehow.
    isv stuck open.boost leak.
     
  3. nickh89GTi Forum Member

    Joined:
    May 10, 2008
    Likes Received:
    0
    Location:
    Exmouth
    Would to much air only cause the problem when it is up to temperature as its fine when its cold? I was thinking it might of been the blue temp sensor [:s].

    Has all new vacuum lines on it. The ISV buzzes nicely when the ignition on but i guess it cold still be stuck open.

    Thanks for your help mate.

    Cheers Nick
     
  4. mk28vICED Forum Member

    Joined:
    May 9, 2006
    Likes Received:
    0
    Location:
    Rugby
    maybe clean the ISV and rubber pipes with inlet/carb cleaner?
     
  5. nickh89GTi Forum Member

    Joined:
    May 10, 2008
    Likes Received:
    0
    Location:
    Exmouth
    Thanks for the input guys. I will give the ISV a clean when i get home tonight to see if that helps. Just had me a bit stumped as its only doing it when its warmed up.

    Cheers Nick
     
  6. moretorque Forum Member

    Joined:
    Aug 26, 2007
    Likes Received:
    0
    Location:
    Reading
    yes because at start up you need more air anyway.
    As the engine warms up the isv should close.
     
  7. nickh89GTi Forum Member

    Joined:
    May 10, 2008
    Likes Received:
    0
    Location:
    Exmouth
    Just so i understand in theory the ISV should only run when the engine is cold and should shut itself off once it is up to temperature? Think i have a spare in the garage somewhere.

    Thanks for your help, much appreciated.

    Cheers Nick
     
  8. Mike_H Forum Addict

    Joined:
    Oct 16, 2004
    Likes Received:
    17
    Location:
    iQuit
    I think the ISV is in use whenever the throttle is closed. Start by checking out your throttle switches next to the cable swivel. You may have a combination of that and maybe an air leak too.
     
  9. nickh89GTi Forum Member

    Joined:
    May 10, 2008
    Likes Received:
    0
    Location:
    Exmouth
    Hi Mike, what is the best way of going about adjusting and checking the throttle switches?

    Cheers Nick
     
  10. rubjonny

    rubjonny Administrator Staff Member Admin

    Joined:
    Oct 31, 2003
    Likes Received:
    2,841
    Location:
    Bracknell
    check the idle switch still clicks when engine hot
    check wiring to throttle switches hasnt snapped
    check throttle cable isnt too tight
    make sure oring on idle screw hasnt gone alowing it to unthread itself
    set up engine as per my faq

    I've had each and every one of the above problems on my car, all caused high/unsteady idle :thumbup:
     
  11. nickh89GTi Forum Member

    Joined:
    May 10, 2008
    Likes Received:
    0
    Location:
    Exmouth
    Hi rubjonney have printed off your digifant tuning guide ready for the weekend.

    When checking the idle switch do i just get the engine up to temp then turn it off at then check for the click or do i need the engine running?

    Have checked the wiring to the switches and idle screw and both seem to be fine.

    Is there a guide on here anywhere for adjusting the throttle cable?

    Thanks for your help much appreciated as its getting rather annoying now. :thumbup:

    Cheers Nick
     
  12. rubjonny

    rubjonny Administrator Staff Member Admin

    Joined:
    Oct 31, 2003
    Likes Received:
    2,841
    Location:
    Bracknell
    the switch should click at any time, cold or hot. only reasdon i mention to check it hot is the problem only happens then, i was thinking perhaps heat expansion was causing issues :)

    throttle cable adjustment is easy peasy, set it so that when your foot is flat to the floor the throttle is just wide open, and that when released it hits the throttle stop on the front firmly. Make sure the linkage is smooth in operation with no binding, on a 16v tb i had i found the main part of the throttle operated fine, but the 'top half' which had its own little spring and actuate4d the idle switch was stiff. This meant the throttlew would close fully no problems, but the upper part wouldnt operate the idle switch! i whipped off the nut on the top and gave it a good clean & lube, there was a bit of crud in the plastic washers. That sorted it!

    Quick n easy check of the throttle wiring is to hold the throttle just off the stop to release the idle switch, say about 1.2-5 rpm. Then press the wide open throttle switch on the top, the revs should drop, then increase when you let go :)
     
  13. nickh89GTi Forum Member

    Joined:
    May 10, 2008
    Likes Received:
    0
    Location:
    Exmouth
    Thanks rubjonny i take it that if the revs don't drop when the open throttle switch is pressed then there is a problem with the wiring to the switches. I already have the wires stripped to the bulkhead.

    With the throttle cable is it best to get someone to hold it fully open than attach the cable and release back to the stop. Think i will give it a good clean and lube it up like you suggested.

    Just when i thought i had sorted it all out and could enjoy driving it again! :)

    Cheers Nick
     
  14. rubjonny

    rubjonny Administrator Staff Member Admin

    Joined:
    Oct 31, 2003
    Likes Received:
    2,841
    Location:
    Bracknell
    yep thats right, both the idle & full throttle switch run off the same wires, just that over 3kish the ecu knows the throttle wont be shut so assumes its at WOT :)

    you could do it that way, i just set it where i think then slowly plant my foot while watching the linkage, then adjust to suit :)

    edit: now i think about it, this could be one cause of the so called 'digilag' if you plant your foot to the floor with the rpm below the cutoff threshold or at a standstill, the ecu thinks the throttle is still shut and tries to adjust the rpm to idle, then when it realises the rpm/afm signal is not showing a closed throttle situation it catches up and goes to WOT running... Hmm.
     
    Last edited: Jul 4, 2008
  15. nickh89GTi Forum Member

    Joined:
    May 10, 2008
    Likes Received:
    0
    Location:
    Exmouth
    Thanks for the info. Will give the suggestions a try later on this evening when i have finished work and report back if its not raining that is.

    I've heard about 'digilag' but i still don't completely understand what it is? :)

    Do you think its worth giving the ISV a good clean out?

    Cheers Nick
     
  16. rubjonny

    rubjonny Administrator Staff Member Admin

    Joined:
    Oct 31, 2003
    Likes Received:
    2,841
    Location:
    Bracknell
    id leave the isv alone unless you have problems, leave it till last :)
    i clean mine out by dipping it in a bowl of petrol or white spirit while its buzzing, leva it plugged in and ign on. Engine cold though!
     
  17. nickh89GTi Forum Member

    Joined:
    May 10, 2008
    Likes Received:
    0
    Location:
    Exmouth
    Hi rubjonny. Finally got a break in the rain this morning so have been out having a look at my car. Pressed the WOT switch this morning whilst engine was running and no change in idle like you said so have swapped the switches for a spare set i had and now the idle drops.

    Checked the throttle cable and seems ok to me. Have been trying to set up the idle as per your FAQ but on the digital rev counter i can't get it to settle on 950 it goes from 900 - 960 them 1020 and back down to 900? [:s]

    Thanks for all your help and knowledge mate is much appreciated. :thumbup:

    Cheers Nick
     
  18. rubjonny

    rubjonny Administrator Staff Member Admin

    Joined:
    Oct 31, 2003
    Likes Received:
    2,841
    Location:
    Bracknell
    thats fine, I set it so the idle flicks between 900-960 :)
     
  19. nickh89GTi Forum Member

    Joined:
    May 10, 2008
    Likes Received:
    0
    Location:
    Exmouth
    Just thought i would check before i went to far with it. Where is the best place to get a CO meter from and how expensive are they?

    Will finish off setting the idle up this afternoon and hopefully all will be well and i can finally enjoy driving it again. :)

    Cheers Nick
     
  20. nickh89GTi Forum Member

    Joined:
    May 10, 2008
    Likes Received:
    0
    Location:
    Exmouth
    Hi guys,

    Have been trying to sort this problem out today as have had a lot of rain recently. I have done everything you have suggested rubjonny but it is still idling high when it is warm. I have cleaned the isv but still the prob persists.

    Strange thing is that idle is fine when getting to 80 degrees, but turn it off then on again and it starts idling high? [:x]. Today i left it for 10 mins buy which time the temp had dropped to 70 degrees and started it up and the idle was pretty much as i had set it up using the FAQ.

    Could this be the symptoms of a failing blue temp sensor (its a GSF one) or do you think its still an ISV problem.

    Thanks for all your help so far guys. Hope i get this sorted soon.

    Cheers Nick
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice