AFN Error Code 00550: Troubleshooting Guide

Hello,

My Passat TDI 1998 / AFN (mileage 271,000 km) has been giving me a lot of trouble for the past few days:

Initially, I was getting no output and an error code 00575.
I then used the search function and helpful tips to discover that the turbocharger boost pressure was gone, and I found two leaky hoses as the cause.
After replacing those parts, a test drive was performed and everything was okay. The boost pressure was back to normal.
No new error entries.

The last two days revealed 2 new problems:

1. Occasional starting problems, both when the engine is warm and when it's cold.
2. Engine misfires with heavy blue smoke during acceleration (mainly when the engine is warm).

I found the error code 00550 17-10, which indicates an intermittent issue with the fuel injection start regulation difference.

VAGcom will then also display the problem:

Injection timing: Actual and target values are completely different.
partially, more than 10 degrees of deviation, and consequently, the engine then also .

Physical examination of the NHG revealed no abnormalities.

'I then took the car to VW, and the master technician also noticed the problem during the test drive. The VAG tester showed code 00550, and the injection start timing was 8 degrees instead of the required 29 degrees.'
while he was coughing and sputtering.

Actuator diagnostics without errors.


According to VW, there is a suspected issue with the crankshaft pulley on the timing belt, as the injection timing is also incorrect. However, if there was a problem, it should have been present for at least 20,000 km since the last timing belt replacement, and it has been running without problems until now?

I once logged data using VAGcom, specifically from group addresses 003, 004, and 011.

Here is an excerpt.

Speed: 3024
Air mass should be 850.
Air mass is 810.
Injection start, target: 9.9.
Injection start: -11.2
Boost pressure, target: 1948.
Boost pressure: 1958.

Measurement protocol as an attachment.

How can we narrow down the source of the error here?
What could be the reason why the setting is so far off?

Best regards from Schleswig-Holstein.

faxe

Did you perform a "basic configuration in MWB 004"?

Will the start of the injection process be roughly on schedule?

If the NHG (presumably a component) is okay, then the next thing to check is the N108, which is the valve that controls the start of injection.

If this happens occasionally, it can lead to this phenomenon.
When it's completely messed up, the injection system sprays so erratically that it's almost frightening. I experienced this once on a 1.7 SDI (AKU) engine.

m;

Hello,

MWB 004 was read out, and it was determined that the start of injection was checked using a VAG tester.
He was selected at the age of 22, but he should have been around 55.

I haven't had any problems since yesterday evening. I went to the gas station, but I didn't get any [fuel/gas].
Biodiesel is used instead of regular diesel fuel.
'Since then, there have been no more interruptions, and the VAGcom diagnostic tool also no longer shows any error code 550.'
Injection start, target vs. actual values, appear to be okay.

The only thing that's slightly lacking at full throttle to reach 770mg is the air mass.

With that, the possibility of a loose crankshaft pulley being the cause of the problem, as suggested by the VW master technician, should be ruled out?

The idea from Dieselmartin might also be a good fit, especially if the fuel injector is not...
'It's working perfectly fine now, and it's running smoothly again with the thinner diesel fuel.'

Should we replace this now, or just wait and see?
I still have the original injectors at 271,000 km. Does anyone have any experience with when it's time to replace them?
which should be replaced as a precaution?

Regards,

faxe

...Even with 271,000 km, I still have the original injectors. Are there any guidelines or experiences regarding when one should proactively replace them?

Yesterday

Best regards,
Rudi

Faxes,

At what speeds and loads did it stall?

I strongly suspect a slowly clogging DPF (Diesel Particulate Filter). When was this replaced?

Something similar happened to me years ago. With almost an empty tank and the use of biodiesel, I experienced exactly these symptoms on the left side of the highway.
Of course. Biodiesel is a bit thicker, and a clogged fuel filter will become noticeable more quickly. As a result, the pump sucks in air, and the fuel injection timing adjuster can no longer perform its function.

Air in the fuel system + late fuel injection = blue/gray smoke...
Definitely! / It's a clear case!

Best regards, Georg.

Hi,

If you've been driving a bio-fueled vehicle, Georg's point is absolutely valid. Especially if you've recently switched to using biofuel.

One more thought, in case the filter is okay:
The insufficient air mass *could* also be another indication of misaligned valve timing, which would support the crankshaft pulley theory. If the pulley was identified as loose during the timing belt replacement but not properly secured, the 20,000 km (approximately 12,400 miles) of operation also makes sense. A poorly installed fitting usually doesn't last much longer than that.

I wouldn't dismiss the possibility of a loose crankshaft pulley as easily.
If the screw is loose, it's possible that the injection timing is just barely within the acceptable range and might be off again the next time the engine is started. It's also possible that this problem is exacerbated by biodiesel, while still working (though barely) with regular diesel.
To be honest, I would double-check my engine and make sure everything is correct because things could potentially go wrong. It's better to check twice; it hasn't hurt anyone yet, right?

Hello,

short feedback on my problem and its solution with the help of the forum

Crankshaft pulley check -> OK, everything is tight.

Checking the injection timing -> at the lower limit of the permissible range.

After replacing the diesel filter and adjusting the injection timing, it has been running for 2500 km.
No more problems.

I assume that the injection timing was occasionally completely off, and then...
suspended the entire regulation.
I don't know to what extent the diesel filter played a role, but it would have been due for replacement soon.

Thank you for the tips.

Regards,


Faxes.