What to look for if you keep blowing coils

Welly

Welly

335D Driver :-)
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Thought I would share my painful and lengthy experience with you all. (Sorry about the over sized images here.....)

Has an issue so annoying it had it's own name and theme music. "The phantom misfire". Anyway, long story short, it was with the APY bolt down pencil coils.

Had a misfire, changed plugs. Went away. Came back 2 days later. Changed coils. Came back 2 days later on cyl 3 after blowing the coil....

This went on and on until I'd eaten 3 coils and decided that something else was wrong. One dodgy coil out of the box isn't unusual. 2 in co-incidence and 3, well no way pedro.

A bit of hunting and advice led me, eventually, to the coil wiring loom. Had a glance, strapped up as usual.... Untill I ripped it all off anyway

loom1.jpg


After an hour of stripping electrical tape back, this is what I encountered...

loom4.jpg


loom5.jpg


loom6.jpg


loom7.jpg


loom8.jpg


As you can see, that wiring is pretty poorly. We strapped it all up with heat shrink for the time being but I am planning to change this part of the loom out in the near future.

Still, many days now without any problems suggests to be that this was the issue. There was visable scorching inside of the heat blanket around the cyl 3 area, indicating a short across the wires.

I believe the part number for the replacment to be 1J0-971-658-L. The heat blanket is 8L9-121-659.

For anyone having this problem, and interested in changing this part of the loom out rather than repairing, this link may be useful.

http://forums.vwvortex.com/zerothread?id=2597240.
 
Last edited:
Nice one Welly, glad you getting it sorted, looks like it will be a bargain buy after all, once all the little bits are done ;)
 
yup ive had to re-solder one of these already.....may strip it away in the summer, thats looks terrible!!
 
nice one dude!

i know the coils aint cheap so this could be a good preventative measure for everyone here, i for one will certainly be inspecting this once it warms up :)
 
how do you get fresh heatsrhrink onto wires that are connected at both ends ?
 
if one were to replace the loom going to the coilpacks, where would it join into the rest of the engine loom?

Mine's just started doing exactly this, I first suspected plugs, but after changing for brand new plugs tonight it's worse! Having disturbed all the coilpack wires in changing the plugs, I'm sure this must be the issue.
 
Prawn said:
if one were to replace the loom going to the coilpacks, where would it join into the rest of the engine loom?

Mine's just started doing exactly this, I first suspected plugs, but after changing for brand new plugs tonight it's worse! Having disturbed all the coilpack wires in changing the plugs, I'm sure this must be the issue.
Click to expand...

Hard to say mate to be fair. Depends on how far back the damage goes. This is generally caused by rocker cover heat, and the plastic cooling and warming regularly. However, was talking to badger5 about it when there the other day, and Bill said that he has found this part of the loom damaged a lot further back...

So..... suck it and see really. Start by stripping the loom back and have a look. Getting it back to the N75 plug is easy enough. Review what the loom is like up until that point and go from there.
 
Cheers man, I've been so lucky with the car up until now I feel, 200k and it's not no 'nasty' problems, everything that's broken has been pretty black and white, like the diff falling out :p

Really hoping this wiring is the cause of my current issue. given it's relation to moving the coil packs I'm thinking it must be.
 
After further research this mroning, I've found the problem isn't there when cold, when the car started to warm up a tad i booted it and it was absolutely fine.

When up to temperature it still seemed OK, but after 30 mins when everything had had time to heat through, the misfire was back again. Seemingly rather intermittent.

I'm going to call audi today about a loom.
 
Sounds familiar! Mine just did it when it fancied doing it. Normally when racing something just to **** me off!!

Also, swearing at the car, and talking about it behind it's back will only make it worse.... :(
 
prawn: i asked audi about a replacement coilpack loom for the s3 and the answer was they only do the seperate loom for the denzels, for our petrol cars we have to buy the whole loom (well the passenger half of the ecu loom anyway) and as welly says that would cost mega bucks, the ones in the states are only like £30

am thinking if there are a few of us needing this loom, might aswell order all together?
 
Cheers for the advice Jonny, I too called Audi yesterday, who said all they can offer me is some coil pack connectors and a pack of new wire to solder it up myself, or a full engine loom at around £550. **** that.

As for ordering from the states, you guys go ahead and do it, but it'll be of no use to me!

Having a 98 AGU A3 it's rather different to the S3 setup, I think my coilpacks only have 3 wires to them for a start.
 
Dude, didn't realise you had an AGU although I should of from threads previous....

Anyway, are you sure it's a loom issue? I mean, have you SEEN the cracks?

On the AGU, as opposed to every other engine, there is an N122 Final output stage chip which controls firing. On all the other engines, the final output stage is built into all the coils individually, except the AGU. This is the main reason why the AGU has very few problems with coil packs going bang.

They aren't easy to get hold of, but if you know someone else with an AGU engine, or can find one being broken, deffo worth a go!

Part numbers for the N122 are 8D0 905 351 or 4D0 905 351. There is apparently a difference between the '8' and the '4' models, however noone seems to be able to say what! My old AGU had the '4' so I suspect your may be the same...
 
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