Coil pack harness replacement

[ExiledWeegie]

hi guys, happy new year

ive just bought a coil pack harness repair kit as ive been getting random misfires for a while and havent been able to sort it and its doing my nut in, ive literally checked everything 10 times, simplified pcv system with silicone hose and aluminium check valve, deleted all the vacuum crap and check valves under the plate, smoke tested whole system and its all sound, done the coils and plugs, also done compression check and still getting misfires on all 4 cylinders randomly so now im onto the coil pack harness.

so ive bought this kit... is it the right one for me? 1.8t 20v auq, i couldnt see anywhere that it tells you what engine codes it works for so just took the plunge for 20 quid. also for anyone whos done this on the auq, the plug has 12 pins, 4 for signal wires, 4 for power and 4 for grounds, does the auq harness have 4 individual ground wires? i havent cut into it yet so just trying to suss it out. thanks for any help in advance.

 

[mty12345]

Here you go mate.

 

[ExiledWeegie]

cheers bud but I have no clue what I'm looking at there lol not great with wiring diagrams and stuff

I went out today and stripped back the tape and plastic conduit and its revealed 11 wires but the plug for the new loom has 12 pins, I found these pictures which makes it easier for me but still a bit puzzled why the pics and layout shows 4 grounds 4 power and 4 signal when I only have 11 wires.

 

[ExiledWeegie]

reviving this thread as I'm still needing help with this.

I cannot for the life of me suss out how to change the coil harness on the AUQ, the plug from new loom has 12 wires which ive tested and it has 4x power, 4x trigger and 4x ground, but the AUQ loom has 11 wires in the loom that feed the coils, chatgpt says just to leave 1 pin free on the grounds but then 1 coil wont have a ecu ground. it looks like this.

coil plugs have...

pin 1 - 12v power pin2 - ecu ground pin 3 - trigger pin 4 - rocker cover ground

new 12 pin plug has...

pins 1-4 - trigger wires
pins 5-8 - ground wires
pins 9-12 - 12v power

so the new plug is simple enough to connect the 4 power and 4 trigger wires but im lost with the ground, the plug has 4 separate ground pins but it looks like the AUQ uses 2 thin brown and 1 thick brown to ground out all the 4 coils and the rocker cover.

anybody ever done this with this repair kit or even have a clue what im on about?

 

[mty12345]

reviving this thread as I'm still needing help with this.

I cannot for the life of me suss out how to change the coil harness on the AUQ, the plug from new loom has 12 wires which ive tested and it has 4x power, 4x trigger and 4x ground, but the AUQ loom has 11 wires in the loom that feed the coils, chatgpt says just to leave 1 pin free on the grounds but then 1 coil wont have a ecu ground. it looks like this.

coil plugs have...

pin 1 - 12v power pin2 - ecu ground pin 3 - trigger pin 4 - rocker cover ground

new 12 pin plug has...

pins 1-4 - trigger wires
pins 5-8 - ground wires
pins 9-12 - 12v power

so the new plug is simple enough to connect the 4 power and 4 trigger wires but im lost with the ground, the plug has 4 separate ground pins but it looks like the AUQ uses 2 thin brown and 1 thick brown to ground out all the 4 coils and the rocker cover.

anybody ever done this with this repair kit or even have a clue what im on about?

Hmm, i'd use a multimeter and check if all the grounds in the new loom are joined together, most likely they are. If so then it will be fine to just connect three grounds and leave one unconnected.

 

[mty12345]

Found this diagram of a different set up, (only 10 wires, 2 grounds)

If you look at the black squares, you will see that all 4 ignition grounds and all 4 cylinder head grounds are joined together inside the new harness, so what i said above looks to be correct, just leave the one ground empty and it will share one of the other grounds inside the loom.

 

[ExiledWeegie]

cheers for the reply, i checked all the wires in the new loom at it has 4 power, 4 ground and 4 trigger,, the rocker cover ground is the only one grounded together inside the loom so without modifying that new loom its useless for the auq, what your saying is right for that loom but the one i bought is different, so looks like the one you posted is the one i need for the auq.

https://www.ecstuning.com/b-ecs-parts/vw-audi-mk4-mk1-tt-18t-ignition-coil-wiring-harness-replacement-1j0971658l/020745ecs01kt/

 

[mty12345]

cheers for the reply, i checked all the wires in the new loom at it has 4 power, 4 ground and 4 trigger,, the rocker cover ground is the only one grounded together inside the loom so without modifying that new loom its useless for the auq, what your saying is right for that loom but the one i bought is different, so looks like the one you posted is the one i need for the auq.

https://www.ecstuning.com/b-ecs-parts/vw-audi-mk4-mk1-tt-18t-ignition-coil-wiring-harness-replacement-1j0971658l/020745ecs01kt/

Hmm that's weird. In that case yeah you could just modify either the new harness by joining the 4 grounds together, or you could just splice into one of the loom side ignition grounds and run the extra ground wire to the plug. No need to by a different harness.

On the OEM wiring diagram all 4 grounds are joined and all 4 powers are joined, it's only the trigger wires that are seperate. So no problem with doing that.

 

[a38L1.8T]

Hello !

I have the burnt-out coil harnesses on my 2001 A3 AUM.
So I ordered the same kit ! I was wondering what you ended up doing?
Did you find 12 wires? Or did you have to make a splice like the original one with the tuning kit, for the for the ground coming from the ECU harness ?

Thanks in advance !

 

[ExiledWeegie]

In the end I didnt have to do it, it wasnt the cause of my misfires, but the harness I posted in the original post wasnt the correct one that I needed as the rocker cover ground point wires didnt lead to any pin in the plug. the one i needed was the ECS harness as it worked out right for my 11 wire AUQ the only mod i wouldve needed was to splice an extra ground to one of the others in the loom.

its a pity youve already ordered it though as I have the ECS harness here still sealed in the wrapper I'd be willing to sell on.

 

[a38L1.8T]

Thanks a lot for the reply, really helpful!

Just to make sure I understand your point about the rocker cover ground: on this kit, coil pin 4 isn't wired to the Deutsch plug, it goes to the ring terminal that bolts onto the rocker cover. As far as I can tell, that does the same job as the factory pin 4 wires (on my A3 they're brown/yellow and run to an earth splice in the harness). The 034 and ECS harnesses also ground pin 4 to the rocker cover, and on the SEAT diagram you posted the factory rocker ground ends at an earth point on the cylinder head cover too.

So my plan would be:
- pin 4: use the kit's ring terminal on the rocker cover, and insulate the factory brown/yellow wires
- pin 2: join the 4 grey grounds from the kit together with the factory brown ground wire(s), since they're not linked inside this harness
- pin 1: the 4 reds to the factory black/purple power wires
- pin 3: the 4 triggers one to one

Would you agree that this works with this kit, or did you see another reason it wouldn't?

Also, out of curiosity, on your 11-wire AUQ, how were the wires split? 4 power, 4 triggers and 3 grounds? And was the thick brown one the rocker cover ground?

Sadly im in France, so for the ECS kit its impossible.

Thanks again!