Let's play a game... guess the problem

SilveR316 · Sep 10, 2008

Ok, I'm pretty sure I have it narrowed down to what it could be, but I'm without a laptop right now so I can't provide a detailed diagnosis.

Symptoms:
- Rough idle, rough engine while cruising at a steady speed
- Only happens when engine is warm, or ambient temperature is warm.
- Engine runs fine until it fully warms up and on cooler mornings
- Engine has a crispier sound than normal which indicates advanced timing (i think?)
- No shuddering while slowing down (no fueling, no shudder)
- Not slow-down shudder symptoms (easily fixed but thats not the problem)
- No shudder under heavier acceleration

After thinking about it, I'm pretty sure it was something to do with the fueling system. Since it seems temperature related (ie. never happens until the engine is fully warm and doesn't happen on cooler mornings or until after the car runs a while and the ambient temperature of the fuel has a chance to rise) I think its one of the following things:

1) Fuel temperature sensor gone south (most likely)
2) Failing injection pump
3) Failing injector/nozzle (unlikely since the race520s are rather new and haven't had any problems in the last 5000km or so since they were installed)

Before I go back to parents place to pick up my laptop and diagnose the problem properly, does this sound like a failing fuel temperature sensor to anyone else?

HopefulFred · Sep 10, 2008

I can't argue against your diagnosis, but I wouldn't be surprised by any temp signal being faulty - air, coolant, fuel, or even MAF.

SilveR316 · Sep 10, 2008

Ok, I grabbed a coworkers laptop at lunch and ran some vag-com stuff.

Fuel temp reports a steady ~38C. Guess we can rule that out as the problem.

MAF values looked fine. Intake temp, coolant temp values looked fine as well. This is a brand new tank of fuel, so I don't think thats the problem either as it was happening on the previous tank as well.

I noticed some air bubbles in the fuel line coming from the fuel filter. I changed the fuel filter a few days ago when I first noticed this problem, but it didn't fix it. Is it possible that there is some other filter somewhere down the line thats clogged? The air bubbles aren't consistent and its only a few every couple of seconds. Otherwise its a steady stream of fuel.

During the rough idle time, I observed that the IQ varied quite a bit. From 1.0 all the way to 8.0. Normally its around 3.4-3.6 when warm.

Timing was reported as dead on/slightly advanced with the engine fully warm.

During the time when the engine ran rough, group 13 showed that the values for the individual injectors changed a bit (I'm assuming it was trying to compensate for the rough idle).

Here are the logs for the individual injectors during a 30s period of rough idle.

Code:

    Group A:    '013            
        Cyl 1    Cyl 2    Cyl 3    Cyl 4

TIME STAMP     mg/str     mg/str     mg/str     mg/str
    0.01    0.19    -0.52    -0.21    0.52
    0.39    0.21    -0.56    -0.16    0.49
    0.79    0.33    -0.61    -0.14    0.4
    1.17    0.31    -0.61    -0.12    0.42
    1.54    0.33    -0.61    -0.14    0.4
    1.92    0.33    -0.64    -0.09    0.4
    2.29    0.33    -0.66    -0.09    0.4
    2.66    0.35    -0.64    -0.09    0.4
    3.03    0.38    -0.64    -0.12    0.38
    3.4    0.35    -0.59    -0.14    0.38
    3.8    0.35    -0.59    -0.14    0.38
    4.17    0.35    -0.61    -0.12    0.38
    4.57    0.33    -0.61    -0.14    0.35
    4.96    0.33    -0.61    -0.12    0.38
    5.36    0.33    -0.56    -0.14    0.4
    5.74    0.31    -0.59    -0.14    0.42
    6.12    0.33    -0.59    -0.12    0.38
    6.5    0.33    -0.59    -0.12    0.38
    6.87    0.31    -0.56    -0.16    0.35
    7.24    0.31    -0.59    -0.09    0.35
    7.61    0.35    -0.56    -0.09    0.38
    7.99    0.38    -0.59    -0.09    0.31
    8.38    0.26    -0.52    -0.09    0.35
    8.76    0.28    -0.42    -0.12    0.33
    9.15    0.28    -0.47    -0.16    0.33
    9.53    0.33    -0.42    -0.24    0.31
    9.92    0.28    -0.33    -0.26    0.33
    10.3    0.24    -0.35    -0.24    0.38
    10.69    0.19    -0.35    -0.24    0.38
    11.06    0.19    -0.38    -0.24    0.38
    11.45    0.16    -0.38    -0.21    0.42
    11.82    0.16    -0.38    -0.21    0.42
    12.19    0.14    -0.4    -0.24    0.47
    12.56    0.12    -0.42    -0.19    0.47
    12.96    0.12    -0.45    -0.16    0.47
    13.36    0.09    -0.45    -0.16    0.49
    13.76    0.09    -0.45    -0.16    0.52
    14.15    0.09    -0.47    -0.14    0.52
    14.52    0.09    -0.47    -0.14    0.52
    14.9    0.09    -0.47    -0.14    0.52
    15.28    0.12    -0.47    -0.16    0.52
    15.67    0.09    -0.49    -0.16    0.52
    16.04    0.12    -0.49    -0.16    0.54
    16.42    0.12    -0.49    -0.16    0.54
    16.79    0.09    -0.52    -0.16    0.54
    17.16    0.12    -0.52    -0.14    0.54
    17.55    0.12    -0.54    -0.14    0.54
    17.95    0.14    -0.54    -0.14    0.54
    18.34    0.14    -0.56    -0.14    0.54
    18.73    0.14    -0.56    -0.14    0.54
    19.12    0.14    -0.56    -0.14    0.52
    19.52    0.14    -0.56    -0.14    0.54
    19.88    0.14    -0.59    -0.12    0.54
    20.26    0.16    -0.61    -0.09    0.52
    20.64    0.16    -0.59    -0.09    0.54
    20.99    0.16    -0.56    -0.09    0.52
    21.36    0.16    -0.56    -0.12    0.54
    21.74    0.19    -0.52    -0.19    0.52
    22.11    0.21    -0.47    -0.24    0.47
    22.51    0.24    -0.52    -0.14    0.42
    22.9    0.26    -0.56    -0.14    0.42
    23.29    0.24    -0.54    -0.14    0.45
    23.68    0.21    -0.54    -0.14    0.47
    24.07    0.21    -0.54    -0.14    0.47
    24.46    0.19    -0.54    -0.14    0.49
    24.85    0.19    -0.54    -0.14    0.49
    25.23    0.21    -0.56    -0.14    0.49
    25.6    0.21    -0.56    -0.14    0.49
    25.98    0.19    -0.56    -0.14    0.52
    26.35    0.21    -0.59    -0.14    0.52
    26.72    0.21    -0.59    -0.14    0.52
    27.12    0.21    -0.61    -0.14    0.52
    27.52    0.24    -0.66    -0.14    0.49
    27.9    0.26    -0.66    -0.12    0.49
    28.3    0.26    -0.64    -0.14    0.49
    28.68    0.26    -0.66    -0.12    0.52

Any ideas?

HopefulFred · Sep 10, 2008

Someone else is going to need to help you. But in the interest of my learning, could you explain what each of the four columns of data is? I see time (in sec) but then I'm not sure what "stamp" means. And why are some of the numbers negative?

SilveR316 · Sep 10, 2008

I believe the numbers show how much each injector must compensate in fueling to maintain an even idle. Not all injectors are built equally, and the fuel pressure required to pop them may be slightly different, in which case the computer has to compensate in order to maintain an even idle.

Someone correct me if I'm wrong, but that's my understanding of it.

It cut off some of the text when I copied and pasted it. "STAMP" actually refers to "TIME STAMP". Marker was a column that was empty. I edited my post above.

cattlerepairman · Sep 10, 2008

Have you tried to adapt the injection quantity when you put the nozzles in?
It may be worth the while to adjust the settings slightly with VAG COM; I had a rough idle (not nearly as severe as what you describe) and all it took was a few minutes of adjusting the IQ. I discovered that I had set the IQ too low with the new nozzles, although it was "within spec". It was fine when the engine was cold (I guess due to the injection time advance in the cold engine and perhaps the IQ is increased, too, when cold) but would just not sound right when warmed up. I increased the IQ and all is well.

SilveR316 · Sep 10, 2008

Yes, I've played with the IQ when the nozzles were put in initially. They were working fine for about 5000km prior to this.

I don't think its an IQ problem as the roughness is not very consistent. I can be sitting at a light, with a perfectly smooth idle. Get going, and stop at the next light and my idling would be rough again.

conejo_a_cuatro · Sep 10, 2008

Hmmmm. This problem sounds familiar. I'll be watching this thread, I hope you find the answer!

MayorDJQ · Sep 10, 2008

SilveR316 said:
Fuel temp reports a steady ~38C. Guess we can rule that out as the problem.

I wouldn't write off the fuel temp sensor just yet...

Try plugging in VagCom first thing in the morning after the car's been sitting all night. If the ambient and fuel temp are equal, the sensor may be OK. Maybe log the fuel temp on the drive to work and see if the temps rise as expected.

As for the bubbles in the fuel line, unless someone installed a second fuel filter, there's no other filter hidden away. Is the plastic T on the filter original? You may want to replace it. I think I paid ~$12 to tdiparts for mine a few weeks ago. The fuel temp sensor is ~$20 from several different vendors.

There were several threads a while back about the "Case Pressure Relief Valve". It's a pretty simple fix, there may be a write up on it some where. With 260k+ miles, maybe this is the issue?

SilveR316 · Sep 11, 2008

Small update.

I don't think the slight amount of air bubbles in the fuel line are a problem. A small amount is perfectly normal (or so I've been told/observed) and the problem still occurs even if there are no air bubbles going through the line.

This morning the ambient air temp was 8C. I was able to make it all the way to work (about 50km) before I even noticed any trouble at all with the rough idle. It only did a small hiccup near the end, but otherwise ran perfectly fine. No laptop with me, so I was unable to scan the fuel temperature sensor.

I'm willing to bet if I start my car at lunch when the ambient temperature rises that it'll start idling rough.

I guess I crack open the cover of the IP this weekend and replace the fuel temp sensor and see if that helps anything.

Edit: I'll also add that it has zero problems starting cold or warm. It fires up as soon as I turn the key, with little or no smoke.

MayorDJQ · Sep 11, 2008

SilveR316 said:
Edit: I'll also add that it has zero problems starting cold or warm. It fires up as soon as I turn the key, with little or no smoke.

Sounds like the pump itself is OK.

gaddman · Sep 11, 2008

Try the Hammer Mod. It fixed my rough idle problem. I had done everything else, even the fuel temp sensor in the IP. Wish I had done the Hammer Mod earlier.

HopefulFred · Sep 11, 2008

I have a hard time seeing this as a mechanical problem. Intermittant drivability issues seem always to be electrical. (in my experience)

What about the EGR? Maybe it's sticking open - or have you turned it off?

SilveR316 · Sep 11, 2008

I have no EGR.

SilveR316 · Sep 12, 2008

Well... took the highway to work this morning... same distance, just faster speeds.

I'm guessing it warmed up the ambient temp of the fuel a lot faster due to driving 130km/h rather than 80km/h. The engine sputtered and completely died right as I was pulling in to the parking lot at work.

I tried to restart it and it eventually did, but not after cranking for 4-5s and a very uneven initial start. Still ran like crap after it restarted.

I gotta drive back to my parents place after work today... which almost double the normal distance I have to work.... I hope I don't have to end up getting it towed or having the engine stall at some intersection....

auto_tech · Sep 12, 2008

Given the injector balance numbers, I doubt it's the injectors. Doesn't look bad enough to make engine stall. I'd look into that case pressure relief valve as well. I think a 10mm wrench gets it out? They do tend to fall apart. I think you can also look in VAG-COM and check desired and actual injection timing. The last faulty pump I found, the actual injection timing went to over 10degATDC under load, while desired timing was still around the 0deg. mark.
I should be in the 'shwa tonight (Taunton and Harmony), I think I even have a spare fuel temp sensor in the car

Drivbiwire · Sep 12, 2008

If you just slapped those nozzles on without calibrating them then that is your issue.

Read this carefully: Those nozzles are hammering the insides of the injectors because your primary injection is occuring north of 400 bar instead of 300 translated, injectors are opening about 1500 psi too late during the pressure rise.

High primary break-pressure hammers the internal rod and mechanisms. The injectors are not designed for opening pressures that high.

Also your IQ values are close to spec/balance, the issue is they are all opening consistently high and way out of spec again pointing to bad injectors (out of calibration).

I see this with EVERY set of injectors that have had Bosch replaced by Bosio. There is no issue with the nozzles its just the fact that Bosio has completely different hydraulic opening characteristics than do the Bosch. This means that Bosch shim settins CANNOT be used with Bosio nozzles, or the other way around.

DB

SilveR316 · Sep 12, 2008

Unfortunately, I won't be in Oshawa tonight (going back to Georgetown straight from Markham, if I make it...).

Drivbiwire, I've read and reread your post 3 times. As far as I can see, you're suggesting that I need to get the injectors calibrated for use with the race520s?

How would that explain everything running perfectly fine for the last 2 months and ~5000km? Also, why is it that the car runs fine after it cools down, and only starts running like crap after driving and warming up?

What are you suggesting I do now? The problem seems to be getting progressively worse the longer the car is running.

auto_tech · Sep 12, 2008

there's plenty of diesel shops, and some forum members locally, that can pop-test the injectors for you. Not everyone can set them up properly if they are out of calibration though.
I didn't realize the Bosio nozzles are that different? Good to know.
Steve's Diesel in Bowmanville tested my injectors (they were ok) and the mechanical part of the pump, they didn't have equipment to check the QA.

SilveR316 · Sep 12, 2008

Ran outside with a coworkers laptop to check if any codes were set after the engine cut out this morning. Came back with this.

17969 - Quantity Adjuster (N146): Control Deviation
P1561 - 35-10 - - - Intermittent

I did a quick search, but I got everything from relay 109 to fuel temp sensor, to a bad IP.

Any ideas?

rdkern · Sep 12, 2008

I didn't go back to search, but what about the fuel filter? It can cause this error.

SilveR316 · Sep 12, 2008

rdkern said:
I didn't go back to search, but what about the fuel filter? It can cause this error.

I just replaced it less than 500km ago. In fact it was the first thing I replaced.

Didn't fix the problem, but it was going to be due for a replacement soon anyways.

rdkern · Sep 12, 2008

Have you checked the fts? Vag that sucker when you know the fuel should be warm.

Second - if dbw suggests having the injectors checked, might be the thing to do if you can't find anything else. Bad injector flow can cause serious engine damage.

SilveR316 · Sep 12, 2008

Alright. Here's a *** moment for you all.

I just drove all the way to my parents place... 80km, almost double what I drive to work.

And not a single freakin hiccup! Engine ran like new, had full power, perfectly smooth, no roughness at all. Someone please tell me I'm not going crazy.

Anyways, right before I started the engine, I fiddled a bit with the wiring harness on the front of the engine (the one right beside the IP). I noticed one of the wires had was soldered, as if it was split apart before. It was the green/yellow one. Does anyone know what that wire is used for?

I'm going to check all the connections in that wiring harness as soon as the engine cools off a bit.

Now that I have a laptop, I'll go check the fuel temp sensor and report back in a bit.

Wingnut · Sep 12, 2008

Check the main plug to the injection pump. There was a very similar problem like this with a member several months back. Initial diagnosis was a bad IP (quantity adjuster). But after examining all the wiring, there was one corroded lead and it was making intermittent connection. Thus the rough idle. I suspected this as soon as I read that your IQ was jumping all around. Then, when I read further and saw the IQ fault, it reinforced my thoughts. Now, with your last post, it looks like you found the problem (wire #5?).

I'll see if I can dig up the thread for reference.

Wingnut · Sep 12, 2008

Here are the threads I was refering to:

http://forums.tdiclub.com/showthread.php?t=203022

http://forums.tdiclub.com/showthread.php?t=202896

SilveR316 · Sep 15, 2008

Thanks Wingnut.

I took apart the whole wiring harness this weekend, but found nothing "funny" in the connections. The wires coming out of the harness where twisted and mangled so I straightened them out and started looking for possible broken wires but didn't find anything.

However, the problem seems to have "fixed" itself. I'm guessing there is a problem with one of the wires going to the harness, but it will be next to impossible to figure out which one it is now.

I guess I'll have to wait until the problem reappears some time down the road and do some more in depth testing then.

Until then... engine is running quite well. Thanks for all the help!

Now I have to figure out why my backup lights aren't working.... heh damn electrical gremlins...

Wingnut · Sep 15, 2008

It could have been the unplugging & reseating of the plug that fixed a marginal connection. Try some deoxit in the terminals next time you have it apart. If you have to guess which wire it is, start with #5. I beleive that is the one that feeds voltage to the quantity adjuster?. That will give you the jumpy IQ readings & the QA fault code you got.

As for the back-up lights. I have had to replace a few back up switches. Its a cheap part and easy to replace on the transmission.

SilveR316 · Sep 15, 2008

Wingnut said:
It could have been the unplugging & reseating of the plug that fixed a marginal connection. Try some deoxit in the terminals next time you have it apart. If you have to guess which wire it is, start with #5. I beleive that is the one that feeds voltage to the quantity adjuster?. That will give you the jumpy IQ readings & the QA fault code you got.

As for the back-up lights. I have had to replace a few back up switches. Its a cheap part and easy to replace on the transmission.

Yeah, the back up switch on the transmission is going to be the 1st thing I'm going to check. Already checked the fuses and bulbs and they're fine.

I started with wire #5 as you suggested as that is indeed the one for the quantity adjuster. It was kind of twisted, but the connection looked good. It's possible the wire is broken on the inside, but I couldn't replicate the problem by moving it around nor testing it with an ohmmeter. By the looks of the wiring schematic in the manual, wire #6 is related to it as well but I found no problems there either.

I cleaned up all the connections, loaded it with dielectric grease, and closed it up.

I'll keep looking, but the engine is working fine for now.

Let's play a game... guess the problem

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