Fuel Injection Timing Off? Get it Fixed!

Hello.

My ALH engine isn't running perfectly; I'm having problems with excessive boost pressure (I've already checked the usual things, like the VTG...).
During a test drive, I also logged data from group 4, and after reading the thread about the start of injection, some doubts arose about the accuracy of the timing setting after the timing belt replacement. (Workshops tend to simply install the belt without making a proper adjustment – only if something doesn't work correctly will they perhaps make corrections).

Okay, here are the values:
First, let's start with idle.
The "should" and "actual" values initially differ significantly and permanently.
Then the actual value is not within the target range (2 to -3) and fluctuates.

By the way: what do +2 and -3 actually mean? (+2 = 2° above OT, and -3 = 3° below OT)?

Time / Speed / Injection start / Injection start is / Duty cycle / -

0.01 903 0.4 1.8 2.8 0.35
1.14 903 0.4 2.2 2.8 1.55
2.35 903 0.4 2 2.8 2.75
3.55 903 0.4 2.2 2.8 3.95
4.75 903 0.4 2 2.8 5.15
5.94 903 0.4 2.2 2.8 6.35
7.15 903 0.4 2 2.8 7.55
8.35 903 0.4 2.2 2.8 8.75
9.55 903 0.4 2 2.8 9.95
10.75 903 0.4 2.2 2.8 11.15
11.95 1050 0 2 2.8 12.34
13.14 966 0.4 2 2.8 13.54
14.34 1050 0 2.2 2.8 14.74
15.54 1449 -1.3 1.8 2.8 15.94
16.74 1701 -1.3 1.1 2.8 17.14
17.94 1785 -1.3 1.1 2.8 18.34
19.14 1449 4.6 2.9 36.7 19.54
20.34 1785 -0.9 1.5 2.8 20.74
21.55 1932 -1.1 0.7 2.8 21.94
22.75 2121 -0.2 0 3.6 23.14
23.95 2352 0 -0.7 9.2 24.35
25.14 1365 -1.3 2.2 2.8 25.55
26.35 1701 1.5 2.6 39.8 26.74
27.54 1764 -1.3 1.3 2.8 27.94
28.74 1785 -1.3 0.9 2.8 29.14
29.94 1806 -1.3 0.9 2.8 30.34
31.14 1785 -1.3 1.1 2.8 31.54
32.34 1785 -1.3 0.9 2.8 32.74
33.54 1806 -1.3 0.9 2.8 33.94
34.74 1827 -1.3 0.9 2.8 35.14
35.94 1848 -1.3 0.9 2.8 36.34
37.14 1848 -1.3 0.9 2.8 37.54
38.34 1848 -1.3 0.9 2.8 38.74
39.54 1890 0.7 1.1 23.1 39.94
40.74 2100 6.8 3.7 84.9 41.14
41.94 2373 7.9 7.5 74.5 42.34
43.14 2667 9.2 9 81.3 43.54
44.34 2919 2.9 9.7 42.6 44.74
45.54 1701 -1.3 1.3 2.8 45.94
46.74 2142 4.4 4.4 63.4 47.14
47.94 2205 0.9 2 52.2 48.34
49.14 2205 -0.9 -0.7 22.3 49.54

I believe the setting is already at its limit with a duty cycle of 2.8 (I've never seen smaller values).

What makes me suspicious is that at 1700-1800 RPM, the injection timing shifts to a negative value (i.e., it becomes retarded).
The deviation from the target value persists even in the mid-speed range.
The maximum duty cycle of 96.4% is reached at time 211.16.

191.96 903 0.4 2.2 2.8
193.16 903 0.4 2.4 2.8
194.36 903 0.4 2.2 2.8
195.56 903 0.4 2.4 2.8
196.76 903 0.4 2.2 2.8
197.96 1848 5.7 4 64.5
199.16 2772 9.7 8.4 89.3
200.36 2226 -0.9 0 9.6
201.56 2457 8.1 7.7 80.1
202.76 3087 11.2 11.4 83.3
203.96 3696 14.1 14.5 85.3
205.16 2457 8.1 4.2 96.4
206.36 2709 9.5 9.5 78.5
207.56 2961 10.8 10.8 83.3
208.76 3234 11.9 12.1 84.9
209.96 3192 0.2 11 2.8
211.16 2436 7.9 6.6 96.4
212.36 2520 8.4 8.4 78.9
213.56 2625 9 8.8 80.1
214.76 2730 9.7 9.7 79.7
215.96 2835 10.1 10.3 79.3
217.16 2961 10.6 10.8 82.1
218.36 3066 11.2 11 84.1
219.56 3129 11.4 11.4 79.3
220.76 3024 -0.4 10.6 2.8
221.96 2583 6.4 -0.9 62.6

A target value sequence is then initiated only in the higher RPM range.

347.94 3339 12.3 12.8 81.7
349.14 3444 13 13.4 84.5
350.34 3549 13.4 13.4 80.5
351.54 3654 13.9 14.1 82.9
352.74 3738 14.3 14.7 81.7
353.94 3843 14.7 15.2 82.9
355.14 2184 -0.9 0 9.6
356.34 2898 -0.2 -0.2 43
357.54 2898 9.2 4 96.4
358.74 2919 10.3 10.8 82.1
359.94 2919 -0.4 0 10.8

If I'm interpreting the numbers correctly, it seems like the idle timing is a bit too early, right?

Have you checked the pump settings yet?

Select 'basic settings,' choose channel 000, and then evaluate fields 2 and 9.

diagram under http://www.ross-tech.com/vag-com/cars/tdi.html or in a specialist article.
or the latest VAG-COM with a TDI timing checker...

Then you'll at least know if the pump is still in the correct position after the timing belt replacement.

CU Gremlin.

Thank you, Gremlin.

Currently, I'm unable to use VAG-Com because I don't have a laptop. Does the timing check function work with the trial version, or is registration required?

Regarding the target values again: How should I interpret positive and negative values in group 4? Positive = before OT (occupancy time), negative = after OT => the larger the number, the earlier?

Holger247 wrote:

Regarding the target values again: How should I interpret positive and negative values in group 4, where positive = before OT and negative = after OT

.
Okay!

Quote:

=> The larger the number, the sooner?

No, but as an amount: the larger the amount, the further away from the origin.

Thank you, Ulf.

Since I'm currently unable to create any new logs, can we estimate from my measured values whether they are incorrect?

At least in the LL (likely referring to a specific engine control unit or system), the start of injection, with a value of 2.2, is no longer within the acceptable range (-3...2), which means it's likely occurring too early.

What impact can this have on engine performance? "Early" timing usually means more responsive acceleration and potentially lower fuel consumption, but it might also result in a rougher idle.

Are there any noticeable effects to be expected in the RPM range of 2800-3000 (under full load)?

Here's the translation:

"The background is this: I definitely get too much boost pressure at full throttle (instead of 1948, it goes up to 2500). Consequently, the fuel injection is sometimes reduced, occasionally leading to a limp-home mode. The error code is, of course, "charge air pressure control difference," which is the typical symptom of a boost pressure system issue."
I've already checked the following: I've "flashed" the VTG (Variable Turbine Geometry) system and applied copper paste (it's working smoothly now without any hesitation), I've inspected the hoses, I've cleaned the EGR (Exhaust Gas Recirculation) valve and even tested it without it, I've replaced the magnetic valves (for the EGR and VTG), and I've checked the voltage supply to the VTG valve. So, I've basically done everything. Unfortunately, the problem still occurs, just before 3000 RPM.
The only noticeable thing about the logged values is the start of injection (the fuel injector was replaced by VW in March). Therefore, I wonder if there could be a connection between the start of injection and the loss of power (which doesn't seem obvious at first glance).

Holger247 wrote:

At least in the LL, the start of injection is actually not within the range (-3...2) anymore, with a value of 2.2 => therefore, it is somewhat too early. What impact can this have on engine performance? "Early" timing usually means more responsive acceleration and potentially lower fuel consumption, but it might also result in a rougher idle. Are there any expected effects within the RPM range of 2800-3000 (at full load)?

Hi,

My pump is also slightly out of adjustment, so that the target value is rarely actually reached in idle mode.
For that, it also starts "optimally" (for AFN standards ).
Your deviation of approximately 1.8° earlier (target = 0.4, actual = 2.2) is, in my opinion, perfectly acceptable in the higher load range, as long as the injection timing is not also at the late limit, i.e., below approximately 5.

Quote:

I definitely get a too high boost pressure at full throttle (instead of 1948, it goes up to 2500). Then, of course, the fuel injection is reduced at some point, sometimes with a limp-home mode. The error code is, of course, intake manifold pressure control difference (the usual boost pressure system). I have also already checked the following: The VTG has been "flashed" and the copper paste has been applied (it now really works without any issues), the hoses have been checked, the AGR valve has been cleaned and also tested without it, the solenoid valves (AGR and VTG) have been replaced, and the voltage supply to the VTG valve has been checked. So, basically, I've done everything. Unfortunately, the problem still occurs, just before 3000 RPM.

It's strange, is the engine somehow modified?
Are all the VTG control hoses completely clear, not kinked, and without any soft spots (especially the section between the air filter, through the solenoid valve, to the charge air cooler)?

If nothing else works, I can only suggest that you adjust the VTG rod in increments of about 0.5 revolutions, making it longer, until the overpressure permanently drops to non-critical values.

Thank you, Ulf.

Quote:

For that, it also starts "optimally" when it's warm

.
I find that it starts much better for me in the cold, but it's still acceptable.

Quote:

It's strange, is the engine somehow tuned?

No, everything is original.

Quote:

Are all the VTG control hoses completely clear and unobstructed

Yes. It also works perfectly fine when "blinking," and it has enough power.
"I also don't experience any problems in the lower RPM range, even under high load, and the issue can be almost precisely reproduced based on the RPM."

The question is how smoothly the VTG (presumably a valve or mechanism) operates. You can definitely feel the spring (you have to apply a bit more force), especially when pressing it manually, but there's no noticeable sticking. When "blinking" (presumably a specific function), it runs absolutely smoothly and rhythmically. It also works smoothly with the syringe, but the 50ml capacity doesn't quite reach the end stop (I obviously have the large loading chamber).

I'd rather not adjust the rod, as it's still set to its "original" position. The goal is to restore the motor to its original condition.

Yes, the LMM (likely referring to a mass airflow meter) is also showing fairly good values (despite 100,000 km). I've seen readings exceeding 1000 (though that was at 2400 mbar). When I look at values at 1900 mbar, I see readings around 850.

It would be possible to monitor the voltage at the solenoid valve, just before the hole. In any case, the control unit is trying to compensate (according to the log), but it's not enough.
Here's the excerpt from the log:

Time, RPM, MAP (specified), MAP (actual), Duty cycle.

479.26 2583 1948 1918 61
480.06 2646 1948 2356 76.5
480.86 2730 1948 2438 87.3
481.66 2793 1948 2458 94.4
482.46 2856 1948 2458 94.4
483.26 2919 1948 2438 94.4
484.06 2982 1948 2387 94
484.86 2940 1204 2275 94.4
485.66 2961 1040 1316 44.6
486.46 2961 1724 1265 29.1
487.26 2961 1948 2091 68.1
488.06 3024 1948 2458 83.7
488.86 3066 1948 2499 94.4
489.66 3108 1948 2458 94.4
490.46 3171 1948 2387 93.2
491.26 3213 1948 2244 93.6
492.06 3255 1948 2060 91.2
492.86 3297 1948 1754 78.9
493.66 3297 1948 1397 63
494.47 3318 1948 1418 61.4
495.3 3318 1948 1499 61.4

Holger247 wrote:

The control unit, at least according to the log, tries to compensate, but it's not enough. Here is the excerpt from the LOG: . . .

Hi Holger,

That's quite interesting.

The duty cycle of 94 apparently represents the minimum pulse width -> the valve is effectively de-energized, yet the boost pressure remains at approximately 1.5 bar for about 4 seconds.
And shortly after, the same thing happens again.

Something must be wrong.
Here are some options that IMO could consider:

1. The external pressure connection to the solenoid valve or the pressure sensor (hose kinked or with a soft spot that is compressed by the external pressure).

2. the solenoid valve itself.

3. Something in the charging mechanism that is cleverly hidden and only reveals itself during manual testing.

4. An intermittent short circuit on the solenoid valve switching wire (highly unlikely).

5. A malfunction in the output stage of the engine control unit, which occasionally fails to respond to the duty cycle signals from the CPU (this is extremely rare in practice).

In my opinion, the most likely options are 3, 1, and 2 (in that order).
If I were in your shoes, I would continue searching there... good luck!