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    Thread: Miss Fire issues and Dying Ignition Modules!

    1. Member
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      '88 ITA Scirocco race car & 2012 TDI Jetta 6 sp. manual
      08-29-2018 08:45 PM #1
      I've been fighting this problem for over a year now. I have a 1988 Scriocco with CIS-E with stock ignition system.
      The car will develop an intermittent misfire that gets worse over time to the point the car will barely run.
      I replace the Ign. Module and it then runs OK but again after a while the same thing happens!
      I have tried various brands of replacement modules, from OEM Bosch, to Merle, to others and they all seem to die, some faster then others.

      This is a car that I race in IT and at this point I'm about to just take it out and shoot it!
      I'm done racing this year and if I can't fix it then I'll sell the car or it's parts and junk what's left.

      Can anyone help me?

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    3. 09-05-2018 03:48 PM #2
      Have you checked power and ground to the module?

      Assuming they are OK I would try a new coil.

    4. Member sdezego's Avatar
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      '90 Corrado | '62 Harley Panhead
      09-05-2018 05:40 PM #3
      Are you using the factory Bosch Cap and Rotor? I have had what seemed like the same issue years ago, but was a result of aftermarket rotor that would start to crap out as it heated up.

      There is a Thick Film resistor on the rotor.

      Also, stock wires, plugs and coil?

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    6. Member
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      '88 ITA Scirocco race car & 2012 TDI Jetta 6 sp. manual
      09-05-2018 09:17 PM #4
      The coil is new, that is I bought it last year when trying to fix the problem and before I replaced the module. The cap & rotor are Bosch OEM and I've tried two different ones.
      All result in the same failure of the module. I was told by a good friend that there may be a voltage spike that may fry the module but where it may come from who knows.
      I haven't touched the car in 3 weeks but I may get to it next week and try some things.

      Either way I am getting rid of the car and moving on to something else.
      Anyone want a good IT prepped VW?
      Tons of spares.
      Many new parts that I bought but never needed.

    7. Member
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      '88 16v SII, '83 Ur quattro, '91 Coupe Quattro, '08 RS4, ’87.5 Coupe GT, '12 Abarth
      09-10-2018 02:50 AM #5
      Have you ever attempted to “cycle the ignition” when this happens? Meaning car is running starts to misfire and you simply turn the ignition switch to the off position and back to the on position (without engaging the starter motor.) While the car is running? (do not remove the key just cycle it. This will keep the steering wheel from locking.)

      If so, does doing the above temporarily solve the problem/misfire? If this is the case then you need a new ignition switch. If I remember correctly it’s fairly easy to get out, small phillips or torx and you can pop the electrical portion out of the back of the ignition housing.

      If there are any cracks on the bezel around the front side (non spade/connector side) of the ignition switch you most likely need a new one. (This can cause the problem your describing and many others that can lead you down all the wrong roads in terms of diagnosis/repair.)

      Older Audi’s also have the problem. Most commonly caused by large sets of keys/lanyards (weight) hanging from the ignition switch/key ring. So common there was the equivalent of a TSB way back in the late 80's for it, when I was an Audi/VW tech in another life.



      techtonicstuning.com/main/index.php?main_page=product_info&products_id=2037

      Also as per: sdezego check the distributor, make sure the connector on it isn't broken, or hanging by the 3 wires it connects to. Make sure there's no oil leaking in from the back of the seals into the distributor from the head. (this will cause misfires as well.)

      Less than $20, well worth a look if it solves your problem & you can sell the car in a good running order and make a buck Shoot if it is cracked and you replace it and it still doesn’t solve your problem, PM me I’ll paypal you the cost of the switch shipped. Happy day!
      Last edited by 8816VSCIROCCO; 09-10-2018 at 03:12 AM.

    8. Member
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      '88 ITA Scirocco race car & 2012 TDI Jetta 6 sp. manual
      09-10-2018 04:55 PM #6
      It's not the switch.

      The problem is the ignition module or really perhaps the voltage it's getting from it's power source.
      They get too hot, and I did test this. T
      hey can get very hot when operating.
      In my case I think to hot and fail or at least no longer perform at 100% since the engine will run but will not rev much past 1-2K.

      I will mess with it soon as I have a "new" module on order.
      I will re-install the old dist. & coil as they are both still good I swapped them out just to discount them as the source of the problem.
      I also swapped out the ECU with a new one that I bought some years ago just to have a spare and again no change.

      I will try a few other things not yet mentioned but I won't list them here unless they somehow fix the issue.

    9. 09-14-2018 09:44 AM #7
      I would second the ignition module

    10. 09-20-2018 04:40 PM #8
      The module is mounted on the heatsink with the proper paste?

    11. Member
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      '88 ITA Scirocco race car & 2012 TDI Jetta 6 sp. manual
      10-26-2018 05:41 PM #9
      Getting back to trying to fix this car as I've been busy with other things.

      I have tried a number of Ign. control modules and all result in the same condition.
      The engine will idle fine but when you try to rev it to past 2K the engine starts to misfire.
      I have noticed the ignition timing seems to be unstable, that is the timing seems to jump around while I hold a timing light on the flywheel marks while I rev the engine.

      Could there be some problem with the "nock box" that would cause the timing to jump around?
      I have tried two different ECMs and two different dist. and the same condition results so I know that they are not the problem.
      I don't have a spare "nock box" so that's why I'm thinking that may be the issue but I'm not sure.

    12. 10-28-2018 08:08 AM #10
      next time it starts misfiring. check the temperature of the coil (see if it's very hot) if it is, then you might have the wrong coil fitted.

    13. Member
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      '88 ITA Scirocco race car & 2012 TDI Jetta 6 sp. manual
      10-29-2018 01:13 PM #11
      The coil is fine.
      I have tried 2 different coils, an OEM Bosch coil that came on the car when I acquired it and a new Bosch coil.
      Both times the engine ran the same.

      I do believe now that the Knock Box is the problem.
      The erratic timing that I see when I use my timing light on the flywheel marks seem to confirm this.

    14. 10-29-2018 11:04 PM #12
      Is there play in the distributor bearing?

    15. Member sdezego's Avatar
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      '90 Corrado | '62 Harley Panhead
      10-30-2018 04:57 PM #13
      This may be an obvious question, but have you tried to unplug the Knock Sensor and see if the results are the same?

      Been eons since I messed with knock box, but I know that bad KS can send the system into limp mode.

    16. Member
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      '88 ITA Scirocco race car & 2012 TDI Jetta 6 sp. manual
      10-31-2018 08:44 PM #14
      I haven't done that but only because I replaced the sensor not more then a couple of years ago so assumed it to be good.
      I'll try doing that and report back here.

    17. Member
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      '88 ITA Scirocco race car & 2012 TDI Jetta 6 sp. manual
      02-10-2020 09:37 PM #15
      Bringing this thread back from the dead.

      After trying to fix this car in the fall of 2018 I got frustrated and parked it the past year and a half.
      Now that I have room in my garage I pulled the car from my trailer and brought it in.

      I had no problem getting it started after it's long sleep but the poor running is still there and no I didn't expect it to fix itself.

      One thing I did observe was that as the engine was idling (About 1200 rpm) I would move the Fuel control box, which is loose.
      When I did this, it caused the wires connected to it to flex, the engine would start to run poor and then smoothly.
      A bad wire in the loom perhaps?

      I swapped out 4 different Ign. Modules and all resulted in the same poor running.

      I ran it today and observed that when idling the revs would vary some, about 2-300 rpms but watching the tack the needle was jumping from near "0" up to as much as 4000 rpms.
      Sometimes when the engine dropped revs it would quit running for a 1/2 second but then come back.
      It also would not rev past 3000 rpms.

      I'm going to start with the tack and work back from there to the Ign. Coil and then further back from there.

      I'm keep looking for the problem and I hope to find it soon.

      I have a very interested buyer for the car but I can't sell it running like this.

      Any further suggestions are encouraged.

    18. 02-11-2020 12:05 PM #16
      would the module get hot if the engine was running really lean? have you tried the fuel pressure?

    19. Member
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      '88 ITA Scirocco race car & 2012 TDI Jetta 6 sp. manual
      02-13-2020 04:56 PM #17
      I have checked the Ign. module on the car when it was running and sometimes they do get quite warm. I believe that a couple of the modules that died on me were due to them getting so hot that the electronics died from it.

      But what would cause that?
      To high of a voltage?
      And from where?
      The alt. puts out a max of 13.5 volts while charging.
      Any high amperage surge I think would melt the wires going into the module if that was happening.

      Due to the weather I haven't worked on it since Monday Fe. 10th.
      I may get to it this weekend as it's supposed to get into the 30's.
      We'll see.
      Wish me luck!

    20. 02-13-2020 05:58 PM #18
      i'm pretty sure the earth wire from the module connects directly to the - battery post. might be worth checking/cleaning that up first

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