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Need Help with VCDS Log

3K views 10 replies 2 participants last post by  The Dub Doc 
#1 ·
I am chasing some ignition timing issues with my Unitronic K04 on my MkV. It's a FSI motor.

Got some logs over the last few days but I need a point of reference on what the numbers should look like on a car that is running well.

*Need a WOT pull from 30mph in 3rd gear if some of you can share your logs. The more logs the better!

Channels I am interested in:

Group 1-0: RPM
Group 3-3: Ignition Timing Angle
Group 20-0: Timing Pull Cylinder 1
Group 20-1: Timing Pull Cylinder 2
Group 20-2: Timing Pull Cylinder 3
Group 20-3: Timing Pull Cylinder 4
Group 30-0: Lambda (Actual)
Group 54-2: Accelerator Pedal %
Group 101-2: Injection timing
Group 115-2: Boost (Requested)
Group 115-3 Boost (Actual)
Group 230-1: Rail Pressure (Actual)
 
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#2 · (Edited)
PM logs and I'll tell you how they look. But keep in mind that the lambda actual and rail pressure actual aren't going to mean anything without the specified values to compare them against. I would recommend instead of trying to stuff everything into one logging session you get one for timing and knock (so include all the timing MBs you have there and add the knock detection MBs), and then do another round of logs with the boost (including waste gate duty cycle - boost control N75 MB) and fueling data (including specified values for the fueling MBs you have mentioned above). All logs should have engine speed and pedal position as points of reference, not just the timing-related logs. Logs should preferably be done in 4th gear from 2K to at least 6.5K RPMs (or redline if you prefer) on the same stretch of road, and with plenty of cool-down time between runs. However, if you don't have any roads nearby where you can top out in 4th gear then 3rd gear will suffice.

Hopefully yours are an exception to the rule but so far out of the dozens of logs I've looked at for folks with numerous different tuners, Unitronic takes the cake for ****tiest logs so far (on cars that don't ostensibly have any issues). Every log I've seen from people with Uni tuning leaves much to be desired. Not saying this to disparage you or your car at all, just saying it so you're prepared in case the feedback is not so great. But hopefully yours will be a different case than the rest I've seen before.
 
#3 ·
The reason I am interested in logs for comparison is because I am very noticeably down on torque, but intermittently. This translated to 20% worse mileage per tank as well. Would be nice to see what a normal K04 should log.

My spark plugs, which are new since 300 miles ago, are fouled and this is what they look like:



Car drove even worse previously, until I discovered a badly corroded ignition coil ground point (this is the common ground for all 4 ignition coils). One ignition coil got cooked during that time, so I replaced all 4 coils and 4 spark plugs. I got rid of all the corrosion and although the car drove better (more low end torque), I am still getting intermittent power issues.

This is what the ground point looked like before I cleaned it.


Usually, the harder I accelerate, the more evident the issue is. If I am on the highway at 70mph and ease into the throttle, the car drives fine. If I am WOT off the line, the engine revs climb but struggles to make power. No wheelspin is possible whatsoever even at WOT.

Things I know from logs right now:
-Rail pressure meets specified
-No misfires
-Boost pressure meets actual
-Throttle body opens up to 99.x% at WOT (no air restrictions)
-Fuel trims are good. 6 to 7% long term. Short term fuel trim is 0.1 to 0.2%
-There are no DTCs
-N75 looks ok
-Timing pull per cylinder between 1 to 2 degrees starting at 4500RPM during WOT
-Plugs continue to be fouled (this is the big one)

This leads me to think a few things because of the excess unburned fuel: 1) my ground cable is still corroded (maybe on the inside), 2) my injectors are leaking and are being commanded at a higher duty cycle than normal, 3) damaged engine harness leading to strange sensor readings and pulled timing-> driveability issues.

Also am not clear if my ignition timing is normal.

Here are two plots:

WOT 3rd gear pull from 30MPH


Another WOT pull from 3rd gear and 30 MPH.
Ignition timing moves increasingly towards TDC until 0 degrees at 3800 RPM, and then advances starting from 3800 RPM onwards. Is this normal?


Will PM you logs as well.
 
#4 ·
#5 ·
There are 2 reasons I asked for logs instead of giving you logs.

1) My setup is quite a bit different then yours and many aspects of my data are going to look different than yours so it's NOT comparing apples to apples

2) I can best help if I get my own look at the situation without relying on the owners interpretation... but that's just best practice, in general. In your particular case you are heading in the right direction with your assessment and you did supply the logs anyway so I appreciate that.

That being said, I'm probably in the minority here but I don't like graphs and plots, I do better looking at raw data. I'm currently responding on my phone and about to go to sleep so I'll have to look at your logs a little more closely tomorrow but at a glance I don't see anything flagrant. Boost curve looks about right for a K04. Rail pressure is obviously fine as you said. I can't speak to lambda since you didn't include both specified and actual (and at this juncture it is very important that I see that so please include with your next post). The timing pull is acceptable. I have to look a little closer at the rest of the timing.

But you're heading in the right direction with your analysis. Your spark plugs do absolutely indicate a very rich condition and this is likely a result of very weak spark because of your bad ground for the coils. I would suspect that issue is still not resolved if the power loss symptoms continue and if the plugs continue to look that way. It also fits your description of the issue being exacerbated as you try to push the car harder.

I'll get back to you tomorrow when I have more time to look in-depth.
 
#6 ·
Thanks. I suspect either the harness is still faulty for the ignition coil ground, or several wires in the harness are damaged and causing this condition. It is very odd that there are no codes.

Looking forward to your thoughts though
 
#7 ·
Apologies for the delayed response and lack of more detailed explanation, work has been zapping my time and my brain power lately.

But to the point... I do not see anything in your logs that jumps out at me nor do I see why you would have significant power loss, I'm still suspicious of the ground for the coils if your plugs are still covered in the signs of unburnt fuel. I agree that it is odd that you aren't getting any codes since one would expect that lack of proper spark would and unburnt fuel would be leading to misfires and thus your loss of power. Have you tried the misfire counter? I suppose it may not report accurately (i.e not be detecting them accurately) if the ECU itself isn't throwing a code (I would expect it would if it knew) but worth a look nonetheless.
 
#8 ·
So I decided to swap in a brand new engine harness. Can confirm that the driveability of the car has improved and is more consistently making power. The only strange behaviours are: 1) The rubber elbow piping branching out from the throttle body pipe popped loose under moderate acceleration. (This hasn't happened since the last time the engine made proper power), and 2) some resistance in the acceleration could be felt as the engine revs past 2500 RPM, regardless of how heavily I tip into the throttle.

I decided to take apart the old harness to inspect it to understand where it went wrong. During my inspection so far, I could see a ton of oil on the harness-side connector for the diverter valve.

When I inspected the terminals on the diverter valve, I also found them to be very oily. The outer body of the diverter valve itself was OK, however. This is Rev. D DV and I never expected it to fail this way. My logs showed that I was holding boost, so I must be missing the whole story. Surely, this means that so much oil made its way into the DV that its internal seals were damaged and caused the oil to flow out through the terminals.

A new Rev. D DV is on the way.

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#10 ·
Soon I hope. Still waiting for my replacement Rev. D DV to come in. (Had to purchase in US since it's 2x more expensive here in Canada)

Also been planning to use some Liqui Moly additives to clean the engine. Have you had any experience with that?
 
#11 · (Edited)
Additives are snake oil. If you use quality, VW 502.00 spec approved fully synthetic oil and change it at regular intervals (5K - 6K max instead of VWs marketing strategy recommendation of 10K), then you will be fine. These additives clean the engine very well on their own. If you want a little extra cleaning action do a short change interval of 1K - 2K miles and then drain it hot. There is pretty much nothing that additives have to contribute that isn't already covered by today's highly "engineered" full synthetic oils.

Edit: Also, yes, I do have experience with some additives. Even though I've firmly held the above belief for quite some time I still decided to try some additives to challenge my notions and see for myself. I have done lab analyses on my used oil since I've had the car so I have a very long-running track record for the trends in wear for my engine, etc. I've used both Liquimoly MoS2 and Liquimoly Ceratec and have seen no noteworthy benefits in wear metals in my UOAs from Blackstone. I conclude that for a properly running and well-maintained engine using top-notch fully synthetic oil these additives have very little or no benefit to add. I believe the same is true of engine flush/cleaning additives. In fact, in some cases such additives do more harm then good. So if you've maintained your engine well and use good oil/filter and good change intervals I don't think you have anything to gain by using any type of additives.
 
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