Leistungsverlust/Nageln/LMM-Werte zu gering AFB | Posts 16+

Hello,
The values seem to be correct (the log is in the first post, under '04'). That's the good news.
'Unfortunately, my TDI has become noticeably louder since yesterday, and I'm now seeing -2.0mg for cylinder 3 and -3.4mg for cylinder 6 in the idle speed control. Driving is too dangerous for me right now, so I'm taking the injectors out for inspection. I can't really explain the change in these values within just 100km; previously, cylinder 6 was at 1.6 and cylinder 3 was at 0.9.'

Regards,
Dieter.

P.S.: Silly question on the side...how are the cylinders counted ?

Hello Dieter,

Could you please post all the fields from measurement blocks 13 and 14?

Hello Michael II,
Here are the values (just measured):
13
-1.7 to -1.3
-0.1 to +0.1

14
-3.1 to -2.7
-1.2 to -0.8
-0.5 to -0.2

It's starting to feel like I have two problems to deal with: the hammering noise (one AJM thinks it's quiet/okay), and the strange LMM values. I've also noticed the following (which isn't as clear in the log):
The LMM (lambda-measuring module) values increase to just below 800 at 2000 RPM. Between 2000 and 2250 RPM, they drop to approximately 600 (including a power dip), and then increase again to around 750 (target value: 879.2).

I think I'm going to have my friend's workshop check the car starting tomorrow. What should they check and in what order (camshaft, valves, injectors, intake manifold, EGR, catalytic converter, turbo...)?

Regards,
Dieter.

Hello Dieter,

Unfortunately, the values for the ESP (Group 4) are incorrect.
Should be: 0..4 (2° ± 2°)

Is: approximately -1.8.

It's also possible that: Did you measure the values for group 4 in "default mode" or just in "normal" mode?

Hello,
The values for the group above were in their default settings (which should be correct, right?), here are the current values:

04: http://www.dhecker.privat.t-online.de/passat/LOG-01-004-xxx-xxx.CSV
08: http://www.dhecker.privat.t-online.de/passat/LOG-01-008-xxx-xxx.CSV
09: http://www.dhecker.privat.t-online.de/passat/LOG-01-009-xxx-xxx.CSV
10: http://www.dhecker.privat.t-online.de/passat/LOG-01-010-xxx-xxx.CSV
11: http://www.dhecker.privat.t-online.de/passat/LOG-01-011-xxx-xxx.CSV

Regards,
Dieter.

Hello Dieter,

Sorry, I probably didn't explain myself clearly regarding group 4.
Group 4 must, of course, be recorded while idling.

If the values for group 4 in your initial post were in their default settings, then they are unfortunately incorrect. This could also be the reason for the undesirable values in groups 13 and 14.
Make sure to have the ESP settings adjusted first. Then, take the measurements again.

Hello Michael,
Could it be that the issue is with the VAG-Com display (-2° from TDC), since under /viewtopic.php?t=3027&highlight=wenn+fr%FCh+klappert it states that the values are correct?

Regards,
Dieter.

Hi,

My (very old) version of VAG-Com always shows positive values for the reading. Only the prefix (v. OT and n.OT) changes.

If you see a negative value with "v.OT" next to it, it probably means a positive value "n.OT". In that case, the value is within the target range.
That would mean we have one fewer candidate for the idle-state power consumption values.

Then I would take a closer look at the valve control system and its adjustment values.
If you can, have a compression test done. You can learn a lot from that.

Hello Michael II,
'I'll ask the guys tomorrow (but I don't think they have the equipment for it). What's bothering me is the change in values within such a short distance (from just under 2 to 3.5 mg for cylinder 6). Should I have the compression checked first, or should I take the head off and have the injectors, camshafts, and valves checked?'

Regards,
Dieter.

PS: How are the cylinders counted?

Hello!

I also have an AFB engine in my A6. It's a 1998 model and has now exceeded 186,000 kilometers.
I'm also experiencing these issues with the air mass and that one very negative value in the fuel injection amount... *sigh*
However, I haven't made any progress with my previous attempts. My initial suspicion was that I had one or more worn-out fuel injectors and a slightly faulty mass airflow sensor (MAF). Since the injectors are quite expensive, I've put that issue on hold for now. Next, I'm going to try installing a different MAF sensor to see if that makes a difference. Hopefully, I can do that this week.
But there's something else. The fuel injection amounts of the individual cylinders changed quite significantly for me after I turned on the air conditioning. With the air conditioning off, the worst value I had was -2.7mg on one cylinder. The others are between -1.3 and ,0.

I will follow the topic with interest and see how it develops. Maybe it will help me a little bit .

Regards,

DENNIS

Hello Dennis,
It's definitely not the LMM in my case (I've tried a 100% tested one), and I'm now getting values as low as -3.7mg on one cylinder, and my car sounds more like a tractor .
Tomorrow, there might be more updates -> We'll be doing a compression test, checking the injectors, and inspecting the camshaft and valves (by the way, the injectors cost about €100 each and are only available from VW/Audi... Bosch doesn't supply them ).

Regards,
Dieter.

Hello,

Perhaps a brief explanation of the values for groups 13 and 14 would be helpful.

Group 13:

Field 1: Injection quantity difference between cylinder 3 and cylinder 2.
Field 2: Injection quantity difference between cylinder 1 and cylinder 2.
Field 3 and Field 4: no setpoint value.


Group 14:

Field 1: No setpoint.
Field 2: Injection quantity difference between cylinder 6 and cylinder 2.
Field 3: Injection quantity difference between cylinder 4 and cylinder 2.
Field 4: Injection quantity difference between cylinder 5 and cylinder 2.

Set Point: -2 mg/H .. +2 mg/H

Positive value:
Each cylinder has a lower power output than the reference cylinder and is therefore supplied with more fuel.

Negative value:
Each cylinder is more powerful than the comparable cylinder and therefore receives less fuel.

Hello,
Here's a quick update:

- Compression OK.

- All Bosch injectors to be tested (Is the one with the needle lift sensor cylinder 3 or 6? -> No one can tell me with 100% certainty how the cylinders are numbered... this is unbelievable!)

- Camshafts with visible wear marks/abrasion -> I have found the part numbers for the replacement parts, is there a special warranty policy for these items (manufactured in 12/99 and with 112,000 km mileage)?

- Intake manifold/AGR with approximately 2mm of carbon buildup.

Regards,
Dieter.

Hello,

Are the track marks deeper than approximately 0.5 mm?

If I remember correctly, the thing about the cylinders is as follows:

Right front: 1, then 2 and 3.
Left front: 4, then 5 and 6.

Hello Dieter, hello Michael!

If I hear that from the camshaft, I get a little scared . Maybe it doesn't look any better in my case....
What can be expected if they are deeper than 0.5mm?
And what could (would) happen if you continue like this?
I think I should get that checked out too... Is it a lot of trouble?

Regards,
DENNIS.

Hello,

For valve lifters with wear marks that are deeper than 0.5 mm, the camshafts must be replaced.
This can cause changes in the valve timing.