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Discussion Starter #1 (Edited)
Q4 ignition problem - solved!

My Q4 has been in the workshop the last couple of months with ignition problems and the mechanic is running out of ideas :( Here is what has happened:

It started running bad on one cylinder (mid-rear bank) and that expanded to all cylinders, ending up with the ignition coils becoming burning hot a few seconds after turning on ignition (the Q4 has one coil per cylinder).

Another engine ECU (Motronic 3.7 for the Q4) has been tested, as well as other coils and a new cable harness for the coils (not from the ECU). This did not change the behaviour when turning on ignition :(

2 months before this happened the timing belt and spark plugs were changed and it ran fine until this happened (no other electrical problems). Any thoughts or suggestions would be much appreciated :)

The only positive thing is that I'm driving the Lancia a bit more and that can bring a huge smile to my face :D
 

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Hi Allan

Sounds like the ignition controller modules (2 black BOSCH units under the air box) are shorted internally. These control the spark to the plug coils under instruction from the ECU.

bob
 

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Discussion Starter #3
Sounds like the ignition controller modules (2 black BOSCH units under the air box) are shorted internally. These control the spark to the plug coils under instruction from the ECU.

bob
What I can see in the diagrams and looking in the car - that is also what the mechanic says - this is not part of the Q4 ignition system.

But thanks for the suggestion :)
 

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OK but I have some questions

Allan, there has to be some kind of switch (amplifier) that provides enough current to the coils to produce the HV spark. Your coils getting hot means that they are being fed current (sizable too to make them hot to touch) at all times -- if the coil output (the spak plug inlet) is directly shorted to ground then I would envision a thermally hot coil. Can you PDF the schematic and post it so I can have a look, or send to me via email?
Did you say that when the car is cold, you can turn the ign switch to RUN position, and the coils get burning hot? ie the engine is not running, the ign switch is in RUN?
bob
 

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The way I have understood it, is that this amplification is "built-in" to the system for the Q4, but how I don't know. The Motronic 3.7 should be the same in the GTV 3L from the 90's, so I will look at the schematics for that as well.

Yes, setting ignition switch to run is enough to make the coils hot. Bob, I have sent you an e-mail.
 

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Discussion Starter #7
Thanks for the info, Lenard. I will talk to my mechanic about it.
 

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My Q4 has been in the workshop the last couple of months with ignition problems and the mechanic is running out of ideas :( Here is what has happened:

It started running bad on one cylinder (mid-rear bank) and that expanded to all cylinders, ending up with the ignition coils becoming burning hot a few seconds after turning on ignition (the Q4 has one coil per cylinder).

Another engine ECU (Motronic 3.7 for the Q4) has been tested, as well as other coils and a new cable harness for the coils (not from the ECU). This did not change the behaviour when turning on ignition :(

2 months before this happened the timing belt and spark plugs were changed and it ran fine until this happened (no other electrical problems). Any thoughts or suggestions would be much appreciated :)

The only positive thing is that I'm driving the Lancia a bit more and that can bring a huge smile to my face :D
I left this same info on your 164 digest post as well. It is the modules that are the problem IMO. I would still check the ignition switch as well even though you changed it 3 years ago just for good measure.
I would have replaced those first over the other items although now that you have all you need is 2 modules and the ignition system is all new.
Make sure the harnesses are clean of corrosion, use dielectric grease on them as well as behind the modules so they get a good ground.

Jason
 

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Discussion Starter #10
Thanks for leading me to the power modules. The schematics have been a bit confusing...

I will talk to the mechanic tomorrow and let you know, when there is progress :)
 

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Q4's with ML 3.7 have the amplifiers build in the ECU and don't have the modules under the powerbox.Take a couple of 6mm2 wires and make good grounds from inletplenum to engine to covers(forward and aft) and try it again.

Arjen
 

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Q4's with ML 3.7 have the amplifiers build in the ECU and don't have the modules under the powerbox.Take a couple of 6mm2 wires and make good grounds from inletplenum to engine to covers(forward and aft) and try it again.

Arjen
I could have sworn all the Q4's had the same ignition system as the rest of the 24Vs. I show all Q4's to have them plus Lenard above with a 1995 Q4 states he has them on his.


Jason
 

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Discussion Starter #13
I also looked at eper and found that picture. Well, tomorrow I will go and have a look at my Q4 - and bring my camera.

The idea with the wires will also be tested, thanks Arjen!
 

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Clarify item

Do not use dielectric grease behind the modules. You need to use thermally conductive paste. These are two different and distinct items. The idea with the thermally conductive paste is that it will thermally couple the ign module (which produces significant heat) to the heatsink upon which it is mounted. Dielectric grease will not conduct heat as well; Jason of course knows this and had a temporary disconnect between his brain and his typing fingers as we all do from time to time!!! The paste I use is called Arctic Silver (since I get it real cheap) but it does seem to work well- I don;t think there is any real practical difference between most of them for this application

Thermal Paste and How To Use It
 

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Do not use dielectric grease behind the modules. You need to use thermally conductive paste. These are two different and distinct items. The idea with the thermally conductive paste is that it will thermally couple the ign module (which produces significant heat) to the heatsink upon which it is mounted. Dielectric grease will not conduct heat as well; Jason of course knows this and had a temporary disconnect between his brain and his typing fingers as we all do from time to time!!! The paste I use is called Arctic Silver (since I get it real cheap) but it does seem to work well- I don;t think there is any real practical difference between most of them for this application

Thermal Paste and How To Use It
Yes, I do know this. In-fact I just used that stuff on my computer the other day after pulling it apart. If you put it back together with he same grease that was on there, it can overheat or not even work. This is the reason I said this (using grease instead of paste) behind the modules.
Why I said the grease was a mistake, thanks for clarifying that Goats! Smart A$$~! Well I do know why, I said dielectric grease on the harness and just well you get it.
Again I am sure this is your problem as stated on the digest. I will now go back an edit that post so that it is clear.

Ciao
 

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@ Jason and Lenard: I posted the 164Q4 productbulletin overhere; 55 pages, 6.7 Mb and in english.

Read page 41 about the powermodules.

http://home.kabelfoon.nl/~avdheide/index_bestanden/Q4 - Product Bulletin.pdf

Arjen

Q4 and TD
Okay. Well I thought that maybe the earlier version had them. I know there are 2 ECU's 0.261.203.301 or 0.261.203.834. Maybe earlier had the modules but from that bulletin it looks like they all are built in. Cool, goo to know. Lenard have you actually looked for the modules?

That simplifies things, either ground like he says or replace the ignition unit.
J
 

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Discussion Starter #18
Another ECU have been tried with the same result, so the electrical system needs to get a thorough check, in particular the ground points. The car has done a lot of miles and have been used as my everyday car for quite a while.

Thanks for all the responses. And Lenard, I would very much like to know what setup your Q4 has!

I'm on vacation now, so not much news in the next couple of weeks, but I will let you know what happens with the situation.
 

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If you look into the schematic, all it could be is a groundingissue.....



The main coil is always under 12V, ground it should have only mometarily.Since it heats up, I think it is always on ground on all the coils
 

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If you look into the schematic, all it could be is a groundingissue.....



The main coil is always under 12V, ground it should have only mometarily.Since it heats up, I think it is always on ground on all the coils
I agree. Man they sure made the diagrams easier.
 
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