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    Thread: Digifant Idle Problems (revised)

    1. 02-28-2003 05:26 PM #1
      This Is a write-up that will hopefully help Digi-Fart around the world
      for 8valve Golfs and Jettas built from 1988 - 1992
      Here was my problem:
      My car's Idle would bounce anywhere from 400-1200 rpm. The car would eventually stall if I didnt babysit it.
      My car would also Buck when I let off the gas and when i would coast.
      A quick checklist of things i had checked while attempting to fix my bad idle/bucking
      -a clean isv
      -a good o2 sensor
      -a good coolant temp sensor (CTS)
      -no vaccum leaks
      -good intake boot
      -good fuel pumps
      -good MAF sensor.
      -good Idle screw O-ring
      -proer ignition and cam timing.
      -good ground wires to the ECU

      The cure? -
      There is a switch on the bottom of the throttle body , It looks exactly like the Full Throttle switch, but on the bottom side of the Throttle body
      This switch is the Idle Switch, it gets pressed in at closed throttle and switches the ECU into its Idle circuit, (minimizes fuel flow etc.)
      As time passes this switch gets moved a little and the linkage cant switch it on anymore so it now has to be adjusted
      How do you know if this problem applies to you? a quick guess is to see if your car stalls when you unplug the CTS :
      The more certain way to check this is :
      1- by listening for the switch to click ( same noise that the full throttle switch makes except you should hear it click as soon as you open the throttle with your hand instead of WOT. ) the engine should be off for you to be able to hear it .
      2- by unplugging the 2 wire harness on the throttle body , ignition on, hook up a continuity tester to the 2 prongs and there should
      be continuity at closed throttle,
      if its not clicking or theres no continuity:
      there are 2 tiny TORX head T-20 screws that you need to loosen so you can adjust the switch to the point where it will be actuated when you let off the throttle.....


      Good luck!



      [Modified by Coupe_88, 10:32 PM 2-28-2003]

    2. Member MidnightGLI's Avatar
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      03-07-2003 03:11 AM #2
      nice write up...
      i'll add my problem/solution to this post.
      my problem goes along with the vaccum leaks, check all your vaccum hoses and replace them all, they are cheap. but when checking for vaccum leaks, don't forget to check the seal at the PCV valve and the valve cover. make sure it's tight and sealed, my grommet was cracked in half and was causing all kinds of havoc with my idle when cold. also check the oil filler cap. i know these are stupid problems, but often and easily over looked.
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    3. 02-17-2005 11:42 AM #3
      Quote, originally posted by Coupe_88 »
      How do you know if this problem applies to you? a quick guess is to see if your car stalls when you unplug the CTS

      What is the expected behavior of the idle if CTS is disconnected?

    4. 02-17-2005 12:50 PM #4
      Lets not forget timing and correct timing procedure with the digifants everybody. If your timing and idle and everything is set correctly your motor should idle at or around 1100 with the blue sensor unplugged. Thats if your timing, VAF, and idle screw are all adjusted properly. After you check all the other problems up there make sure to time your car right. Get the timing adjusted properly, connected the sensor rev it three times over a 3000 let it sit and check the timing again. I usually do it twice just to make sure. Besides all that digi's just seem to have bad idle tendencies. A digi that idles perfectly should be put into the Smithsonian because it would be truly a feat of science.


      Modified by adub96 at 12:54 PM 2-17-2005

    5. Member Black_cabbie's Avatar
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      02-17-2005 12:56 PM #5
      Quote, originally posted by Cab42 »
      What is the expected behavior of the idle if CTS is disconnected?

      Depends if the car is cold or hot. If it still cold and you unplug it will probably die. Slowly with a lot of sputtering and coughing.
      If its hot and you unplug it the idle will change a bit. I think it goes a bit higher than normal.
      Chip Tuning for a living @ www.microchips-tuning.com

    6. Member Mortal_Wombat's Avatar
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      02-17-2005 01:00 PM #6
      another way to cure a the same problem with a different cause is to set the idle with both the blue cts and the ISV disconnected
      if the car can idle wiht out both of those it sure as hell can idle dead on with the isv connected (its how my car is setup and it idles like a freakin dream)
      N I N E - F O O T E R S
      @a2alpine WTB: OBD1 ABA short block, must have oil squirters.

    7. 02-19-2005 02:03 AM #7
      I was surprised to learn that even w/o an IAC, my car idles beautifully when the idle switched is (manually activated). prepping the car, originally CIS now digi II, for MSnS... can anyone tell me how the digi system controls the idle speed?? is it timing? fuel? or both?
      edit: I know the timing is varied to maintain idle... I guess I'm just wondering if the fuel is also used to control it.
      Thanks!


      Modified by joelmahoney at 2:04 AM 2-19-2005

    8. Member quadmodrophenia's Avatar
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      02-19-2005 09:46 PM #8
      Anyone want to tell me where I can get the o-ring for the idle screw on the TB? I can't match one up anywhere that fits proper like.
      So many problems taken care of when I yanked the ISV and re-routed it. Now all I have to do is get that damn o-ring so my idle doesn't change itself after some "spirited" driving.

    9. Geriatric Member VDub2625's Avatar
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      02-19-2005 10:35 PM #9
      Just go "borrow" a whole screw from the junkyard

    10. Member quadmodrophenia's Avatar
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      02-19-2005 10:53 PM #10
      Funny, that's exactly what my parts guy said at the dealer

    11. Member monoaural's Avatar
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      05-14-2005 02:18 AM #11
      Would this work for CIS-E engines also? I have a 86 golf, with the same symptoms.
      -Jon

    12. 07-06-2005 08:10 AM #12
      While all these things sound great, the Idle Control Valve is usually not the problem. What is almost always bad is the throttle plates (or butterfly valves) inside the throttle body. Over time they get gummed up, especially inside the pivot pin area (the place where the valves fit inside the throttle body). The secondary valve (the small one) gets stuck slightly ajar and gives the car 'false air,' leaning out the mixture, and making the car hunt for a good idle. The easy solution is to buy a new throttle body....but since that is very expensive, the next thing is to do a "rebuild" of the throttle body. It's just really a disassembly, cleaning, and reassembly. Take some digital pictures or make some drawings as you go. It's not too hard. There is a spring or two that can be tricky to put back on the throttlebody, but they are big and not easy to break or lose.

    13. Member Black_cabbie's Avatar
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      07-06-2005 07:33 PM #13
      I did the TB "rebuilt" too, and I saw a difference in throttle response and a better smoother idle.












      Chip Tuning for a living @ www.microchips-tuning.com

    14. Member MK2SnowPilot's Avatar
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      10-06-2005 10:37 PM #14
      Quote, originally posted by Coupe_88 »
      This Is a write-up that will hopefully help Digi-Fart around the world
      for 8valve Golfs and Jettas built from 1988 - 1992
      Here was my problem:
      My car's Idle would bounce anywhere from 400-1200 rpm. The car would eventually stall if I didnt babysit it.
      My car would also Buck when I let off the gas and when i would coast.
      A quick checklist of things i had checked while attempting to fix my bad idle/bucking
      -a clean isv
      -a good o2 sensor
      -a good coolant temp sensor (CTS)
      -no vaccum leaks
      -good intake boot
      -good fuel pumps
      -good MAF sensor.
      -good Idle screw O-ring
      -proer ignition and cam timing.
      -good ground wires to the ECU

      The cure? -
      There is a switch on the bottom of the throttle body , It looks exactly like the Full Throttle switch, but on the bottom side of the Throttle body
      This switch is the Idle Switch, it gets pressed in at closed throttle and switches the ECU into its Idle circuit, (minimizes fuel flow etc.)
      As time passes this switch gets moved a little and the linkage cant switch it on anymore so it now has to be adjusted
      How do you know if this problem applies to you? a quick guess is to see if your car stalls when you unplug the CTS :
      The more certain way to check this is :
      1- by listening for the switch to click ( same noise that the full throttle switch makes except you should hear it click as soon as you open the throttle with your hand instead of WOT. ) the engine should be off for you to be able to hear it .
      2- by unplugging the 2 wire harness on the throttle body , ignition on, hook up a continuity tester to the 2 prongs and there should
      be continuity at closed throttle,
      if its not clicking or theres no continuity:
      there are 2 tiny TORX head T-20 screws that you need to loosen so you can adjust the switch to the point where it will be actuated when you let off the throttle.....
      Good luck!

      Another good and VERY quick way to test it to unplug the wires and connect a test wire between the two - simulating the "Idle" condition for the ECU. If This makes a difference it's most likely your problem!

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    15. 05-16-2006 09:53 AM #15
      Hi and thanks for this information. I have been searching for answers and this is the first specific info about an idle switch issue that I have found. I will try it. I have another question. Does a malfunctioning idle switch cause sluggish acceleration? The problem my 90 8V(RV) is having is sluggish acceleration and when it does this it almost always idles rough(lots of vibration) and some times will hang high around 1300rpm then come down. seems to be affected by air and engine temperature. Worse when warm. I have replaces temp sensor, O2, checked and cleaned Idle Stabilizer and put in new plugs. Occasionaly it will run perfect for about 15 minutes when cool then back to sluggish and rough. Any thoughts? What about MAF?

    16. Member nofx1981's Avatar
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      10-23-2006 09:26 PM #16
      Quote, originally posted by taskahead »
      Hi and thanks for this information. I have been searching for answers and this is the first specific info about an idle switch issue that I have found. I will try it. I have another question. Does a malfunctioning idle switch cause sluggish acceleration? The problem my 90 8V(RV) is having is sluggish acceleration and when it does this it almost always idles rough(lots of vibration) and some times will hang high around 1300rpm then come down. seems to be affected by air and engine temperature. Worse when warm. I have replaces temp sensor, O2, checked and cleaned Idle Stabilizer and put in new plugs. Occasionaly it will run perfect for about 15 minutes when cool then back to sluggish and rough. Any thoughts? What about MAF?

      That sounds exactly like the problems i'm having, havnen't been able to find the problem, it's really f'n anoying, plz lemme know if you find the problem

    17. 10-24-2006 08:36 PM #17
      holy shipballs batman! I havent viewed this forum for 2-3 years ( i posted this topic 3 years ago ) and I just came to pop in and what do I find, one of my posts lingering on the list of topics hah!
      Taskahead: No, the idle switch circuit is open off idle and has no effect on performance, it simply just tells the ECU " Hey! digifook!, do your idle thing!" This car does not have a TPS ( throttle position sensor) which tells the ECU things at any/every point of throttle travel which makes it easy to diagnose things on our cars , its just a WOT and an idle switch. As for your poor running while the car is warm you are experiencing some bad inputs from your sensors ( CTS, O2, possibly Vane Air Meter (what you called a MAF)) meaning that your car is going to run pretty smooth while it is still in open loop mode but when the engine and 02 sensor warm up and it switches to closed loop, then the computer actually clocks in for the day and goes to work thinking its doing a good job but it cant because its tools ( the sensors ) are telling it lies, Its the same kinda thing like when you tell your mom or your wife that you are out of toilet paper when you actually have 5 rolls and then she goes and gets a whole bunch more toilet paper and then you end up with more than you need and with an engine, that equates to crap.
      -_-_-_-ASSUMING that your 02 sensor was wired in properly ( soldered well, clean connection) that there are no air leaks before the o2 sensor ( ex. manifold leak)
      and that you put good spark plugs that have been gapped correctly and base ignition timing is set properly to 6 degrees advance and that your coolant temperature sensor is good along with the wiring for it. I can recommend a couple things.
      1-Seafoam
      2-Clean , repair, replace groundwires. Make new ones if necessary. I like to put a new one from the negative terminal to the tranny , then to the top of the valve cover, and then from the ecu case to the chassis. this will clean up the performance/response considerably if your grounds are like most 20 year old VW grounds.
      3-Might as well try a different Airflow meter, borrow one from a friend while he isnt looking and see if it reacts differently.
      Let us know what happens -Coupe

    18. 11-16-2006 01:24 AM #18
      Wow, all I can say is THANKS!!! Finally had it with my Golf reving as it feels fit, anywhere from 800 up to 2500 then down to almost stalling. Even in traffic if you just started to go and put the clutch in, it would rev up to almost 3K. Well, i took all your advice and went at it tonight. I took the throttle body off and completely cleaned it out, Regapped and cleaned the plugs (till I get newe ones) Cleaned the ISV AND fixed my idle switch which wasnt being pushed.
      I took it out for a spin and its like a new car! It stayed at 800 whenever not driving. No dips, bounces, rev-up, NOTHING!
      Thanks again for everyones great advise on here. I'm actually looking forward to my comute tomorrow. You guys rules.

    19. 02-01-2007 01:48 PM #19
      Does anyone have a part number for the Idle Switch? Having a hard time locating something. I have a number here, but I'm not sure if it's correct: 037-133-093D
      My dealer says this switch is bad. (Doesn't make sense since the car shows these symptoms only part of the time.) Any help is greatly appreciated.
      BTW...this is a great forum...glad I found it!!

    20. Member Gede Nimbo's Avatar
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      10-10-2007 06:46 PM #20
      My 91' Digi 2 Golf 8V has a problem with cold idle when started up. It will not idle above 400 rpm and runs rich until it warms up a bit then idles at 900rpm which I set it to. I'm at my wit's end with this engine and will go onto 16V Digi 2 soon but I wanted to drive the car on the 8V first. Where do I start my investigations,
      replaced HG, intake, exhast gaskets, ported Digi 2 head
      I checked all the electrical connections/plugs and cleans
      Cleaned ISV,
      Cleaned MAF
      replaced the black coolant temp sensor
      flushed coolant and radiator
      Installed Low temp fan switch and T stat (Car runs a bit hot before the fan cycles)
      New head gasket

    21. 10-11-2007 04:53 PM #21
      do you have to take the TB off too adjust the idle switch on the bottom? I cant seem to get a screwdriver or anything else on there with it on!!!

    22. Junior Member XLJesse's Avatar
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      11-09-2007 05:14 PM #22
      my car recently has been being a bitch.... i recently put in a new ISV because my old one was busted, since i put in my new one its been doing some real funny things i dont know if it has anything to do with the ISV even its been raining recently aswell
      Its been idling better, but now at some red lights it just bouncing from literally 200 rpm where the battery light flickers on because it almost shuts off and then it jumps up to about 1500 and then bounces up and down then shuts off. I have checked all my sparks plugs and wires.. i also i have sprayed around the valve cover with carb medic checking if it was leaking in the seal and nothing. Vacuum hoses and everything seems to be all intact good no vacuum leaks i think its a fuel problem but i dont know what... also i will be driving and accelerating quite fast, and all of sudden it will just decelerate it will have no pull whatsoever but still reving at a high rpm just not giving any power

      i know this is probably seems like alot but any info or anything would be great. if you i can give more info let me know ill do my best.

    23. 11-10-2007 01:04 PM #23
      check the idle switch under the t-body. i didnt even have to loosen the screws to change your symptoms on my car. just reach under there and push the switch towrds the stop.
      i did it to my car which was doing the same things. you pull up to a light and let go of the gas and the revs fall down to almost stall. then it hunts to keep running. i have also had issues while driving on the hiway like what you mentioned about loosing pwr. try that switch adjustment......hey its free

    24. Junior Member XLJesse's Avatar
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      11-16-2007 04:38 AM #24
      no doubt thanks man!

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      11-30-2007 09:51 AM #25
      Quote, originally posted by Coupe_88 »
      Here was my problem:
      My car would also Buck when I let off the gas and when i would coast.

      mine seems to be bucking/losing power at really low throttle inputs under load.
      Seems fine if you goose it... but part throttle is weird.
      I'm sure my ISV is bad... I'd been having issues with it starting and keeping started when it's cold. Under normal circumstances, when you let off the gas it would dip well below normal idle speeds and bounce. It would also buck hard at lower RPMs.

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