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Miss Fire issues and Dying Ignition Modules!

4K views 20 replies 7 participants last post by  DbilasTDI 
#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?
 
#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.
 
#5 · (Edited)
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!:beer:
:popcorn:
 
#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 ·
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.
 
#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.
 
#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.
 
#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!
 
#19 · (Edited)
Worked on the car some this past Sunday.
Didn't find any one thing that helped the car run better.

I moved parts of the wiring harness around that connects the Ign. Module, the Knox Box, and the OX Box to check for faults in the wires.
At times this seemed to effect how the car idled and other times it had no effect.

After a while the car did idle smoothly by adjusting the idle air/fuel at the duel dist. and the base ign. timing.
This had no effect with how the car stumbled when I open the throttle.
The revs would rise just a bit before it started to miss fire.
I also noticed a it back fired a few times.
I also noticed the engine is going full lean when this occurred per the Wide Band O2 meter.
I'm going to now look at the fuel system as a possible problem for this poor running.
I'll check the electronic controls and wiring for faults the next time I have time I work on the car.

FYI

If I don't find the problem soon I think I just part the car out and junking what doesn't sell.

I need to move on to other car projects that have a future with me, this one is almost done!
 
#20 ·
Car starts and idle but doesn’t rev, is it possible your primary fuel pump is not delivering the correct pressure. Certainly there’s an issue with the ignition control module, but usually when they fail, you end up with a no start condition.


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#21 ·
Your fuel plunger can gunk up especially if the car is not driven. IT sticks and wont allow more fuel. remove the plunger by the book and try cleaning it up, and replace by the book. Techron can remove this over time and multiple tanks, but it sounds like you may be needing more.
 
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