Misfire - Coilpacks and Plugs changed. 1.8T AUM

[RickkyP]

Hoping someone can help me try and sort out whats the most likely cause of this problem, I've been reading the forums for ages but there seems to be so many potential things, I'm hoping someone can narrow it down!

A few months ago I got a misfire from the engine, the the proper car almost undriveable type. I got the nearest garage to replace the coilpack that was faulty (number 2), all good. A few weeks after another went, so I ended up changing the rest of the coilpacks to make sure it wouldn't reoccur.

Then recently I've been getting an engine management light, VCDS lite brings up the following error codes:
17705 - Pressure Drop Between Turbo and Throttle Valve (Check D.V.!)
17763 - Cylinder 1 Ignition Circuit: Open Circuit.
17769 - Cylinder 3 Ignition Circuit: Open Circuit
17772 - Cylinder 4 Ignition Circuit Open Circuit.

Interestingly the cylinders throwing up problems are the ones I replaced, I just used the ones Euro Car parts supplied, I can't remember the brand. The garage fitted part however looks identical, even down the colouring of the plastic on top and was the exact same price I paid so I assumed it would be the same part.

Any thoughts on what could be causing this? I've got a silicon TIP to fit, hoping the pressure leak is from around there somewhere, I already replaced all the EGR pipes which had pretty much disintegrated.
Not sure whats causing the misfires.

Physical symptoms I've noticed, are as the car comes onto boost, it comes on strong, backs of a bit then comes back, its most noticeable in 2nd gear, but as accelerating through the rev range the boost level feels like its fluctuating, so the car pulls harder then less, harder then less.
I've checked the resistance on the N75 valve, and its 30ohms.
When I reset the errors by disconnecting the battery it usually takes until the 2nd drive in the car before the error light comes back on.

The car is a 2001 1.8 8L AUM model. Any help much appreciated!

Edit: If its relevant, I only seem to get 22-28mpg, and thats 60 motorway miles every day. Not sure if thats normal or not.

 

[S3 Hilife]

The first fault looks like a leak somewhere or faulty DV, check tip and vac lines under inlet manifold for splits first.
Have you inspected the coilpack wiring harness for splits and cracks which is very common on these cars and may be worth replacing anyway for piece of mind.

 

[RickkyP]

Thanks, the piping all looks good, but I'll remove it all when I do my TIP and replace what I can with silicon.
No, I'll check the wiring on the coilpack. Thanks.

 

[S3 Hilife]

You can also carry out a simple test on your DV when you take it off to change your tip, press the diaphragm up from the bottm and place your finger over the vacuum port, if it holds in place it is ok, if it returns then bin it and replace. Simple but effective

 

[RickkyP]

I've had a very basic look at it now and while it looks pretty mucky, and manky. There is no obvious cracking of the insulation or damage.
It seems odd that the 3 misfire errors I am getting are on the coilpacks I did. I think I'll swap number 2 with 1 and see if that moves the error codes around.

 

[badger5]

coil pack wiring ok? not the usual insulation shrinking and cracking?

 

[RickkyP]

Didn't get a chance to it last night as the rain was pretty bad. I'll go over it with some WD40 and a rag to see if I can spot any cracking and shrinking under the muck.

 

[RickkyP]

Ok had a look and its looking worse for wear, signs of loom deterioration, insulation missing cracked etc. I notice Awesome GTI do a replacement, is this a case of unplugging the old one and plugging in the new one, or soldering bits and pieces into place?
I've swapped Cylinder 1 and 2 coil packs as it seems odd that the one that I didn't buy the coil pack for myself is the OK one, especially as the wires into the plug for Cylinder 2 actually look worse than the others.

I've had a really good look at the dump valve piping and the only thing that looked like it could be potentially leaking was the hose to the top of the dump valve, the factory hose clip wasn't very tight and I could pull the hose off with it still on. I've reinstalled with a new hose clip and I'll see how that goes.

Edit: Well either the hose clip or something I've tightened up when I reassembled the pipework has made a difference, no surging on and off boost now and far less turbo noise, in fact I can barely here it. Just the misfire to deal with now, waiting to see if my check engine light returns.

 

[mark_S3]

To replace the Coilpack wiring loom, it's basically a case of match the exsisting to the new, then cut and splice into a the loom at a point where there's no damage to the loom.

Mine was cut and spliced into the exsisting loom as its starts falling down side of the block near the TIP.
Them each wire was solder then protected with heat shrinking.

Match up the corresponding wire from old to new. Do one wire at a time until there all done.

 

[mark_S3]

I purchased my loom from AwesomeGTI.
It's one listed for 1.8t. Don't worry about any listings about engine codes.
Your only using a suitable length of wire from the connection to coilpack, which you will cut off and tap into exsisting.

 

[RickkyP]

Ok, so I've been driving a day or so.
After initially seeming to have been fixed the leaking pipe seems to have returned, the car is very surgey on boost again and I can hear a lot of turbo noise. Also the same error code regarding the pressure loss is back.

I checked the diverter when it was off the car, it held pressure no problem and the spring still seemed very strong.
After swapping the No2 an No1 coilpacks I'm not getting a misfire on all 4 cylinders.
Since the coilpacks are new (last few months) and the loom does look a little tired, is this the last port of call? Anything else I should check or should I go and spend money on the loom? (*cry*)

Also a long shot, but does anyone know a garage in the Hull area that could smoke test the pipe work and who are pretty good with these engines. (I'd rather someone who already knows the likely causes than someone starting from scratch)

 

[IPG]

You can also carry out a simple test on your DV when you take it off to change your tip, press the diaphragm up from the bottm and place your finger over the vacuum port, if it holds in place it is ok, if it returns then bin it and replace. Simple but effective

so with this test - i've pushed the diaphragm all the way up, put my finger on the end, the piston moves down (but doesn't stay where i pushed it to), i release then i can hear the diaphragm close = replacement or still ok?

 

[RickkyP]

Ok so I spent (wayyy to long) today changing the loom, definitely not a job I enjoyed! Also did the rocker gasket whilst under there to sort out some oil seepage.

Took it for a drive and while it does seem slightly better, I'm still getting the boost surge fluctuations on full throttle, but more disappointingly my check engine light is back with the same error codes:

17705 Pressure Drop between Turbo and Throttle Valve
17763 Cylinder 1 Ignition Open Circuit
17769 Cylinder 3 Ignition Open Circuit
17772 Cylinder 4 Ignition Open Circuit
18010 Power Supply Voltage too low (assume this is because I had battery disconnected)
17766 Cylinder 2 Ignition Open Circuit

Back where I started! Whats the next port of call to check?

Oh and for some reason the air cons stopped blowing cold as well since I did it!

 

[Tfsi gone]

I take it the Sparks are fine?
Maybe the air conditioning has packed in due to Sod's law...

 

[RickkyP]

Sparks plugs replaced a few weeks ago, loom replaced today. Coil packs about 2 months ago.
Can't find any obvious hose leaks either, had everything off and on again.

Its driving me mad haha, I just want that damn engine management light off.

Is it possible that the coilpacks as they are just the cheap ones that Euro Car Parts offer are causing an error even though they're fine?

 

[Tfsi gone]

Very much doubt it mate. Have you reset the codes and see what happens after. Reason I asked is I changed parts on my B8 however without resetting the car it didn't know I had done it if that makes sense..

 

[RickkyP]

Yeah, the battery was disconnected whilst I did the loom, which took about ten hours by the time I'd done a few other jobs. (Also i had a heck of a job getting the plug pin connectors out)

It did what it always does when I reset the errors, first drive its ok, no warning light. Second time I start up the engine light always comes back with the same codes.