Cold start problems with BLS 1.9 TDI engine

Hello everyone,

I have a 2007 A3 with the BLS engine. It's a rebuilt engine that I installed myself. It was a direct replacement because the car previously had a problem with the crankshaft at 200,000 km. I took over the engine parameters and re-calibrated them. The water pump was already installed.

VCDS is available. No piracy...

How does the support account system work here? I don't want to buy VCDS twice...

The vehicle is running well overall and has already been driven 300km since the mentioned modifications. The vehicle has a new technical inspection (TÜV). After the modification, the battery is new, and the glow plugs are new. Error memory is empty.

However, within 10 seconds of starting, it exhibits fluctuations in RPM and jerks significantly. After 10 seconds, the problem disappears. The behavior is not observable during a warm start.

The twist angle is -2.9°. Since I still have a Golf with the same engine, I compared the values again, and here too, the twist angle is -2.9°. However, this one doesn't exhibit the same problems.

Okay, here's the translation:

"My question now is, how can I proceed to find the problem? Which control module should I look at? I also only found information about the twist angle online. Maybe someone can explain to me what that angle is all about. VCDS shows me target values of -6 to 6 here. I'm wondering why it's required that it be at 0." There's a reason why tolerances exist...

Thank you for your support.

Hi, please read the terms of service.

Hello.

Quote:

However, within 10 seconds after starting, there are fluctuations in the speed and it jerks a lot. After 10 seconds, the problem is gone. The behavior is not observable during a warm start. The twist angle is -2.9°. Therefore, since I still have a Golf with the same engine, I compared the values again, and here too, the twist angle is -2.9°

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I would adjust the -2.9° KW reading to be within +/- 2° KW, ideally around ~0° KW. However, I don't think that's the underlying problem. The engine simply runs better and more efficiently when properly tuned.

You mentioned you have a video of the RPM fluctuations. Please upload it here in this thread so we can see if the fluctuations are "soft" (due to air in the fuel supply) or more "hard" (due to loose connections in the control of the injectors or control issues).

Quote:

This behavior is not observed during a warm start.

The coolant temperature sensor is often faulty or shows fluctuating readings in these engines, and it's also very inexpensive. First of all, I would simply replace it (it costs about 10 EUR and takes 5 minutes of work).

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It is a reconditioned engine that I installed myself.

Are the PD elements identical to the previous ones? They must be compatible with the engine control unit, which may not be the case depending on the year of manufacture and any modifications made in between.

Best regards, Rainer.

I'm interested in knowing what kind of crankshaft damage you experienced. Connecting rod bearing failure due to worn connecting rod bearings?
We also have a BLS in the family. However, I know of one with over 300,000 km on it, and it's still in perfect condition. I've also heard of connecting rod bearing failures in the BLS engine quite a few times.

When you replaced the PD elements, you certainly used new O-rings, right? Did you also smooth out the burr that forms in the chambers due to the one-sided screwing? "It's not that the O-rings have been damaged, but it might leak a little if it's left standing for a long time."

Hi,

I installed the PIDs from the defective engine. That is, they are the ones from the faulty motor. The MSG has aged.

The seals are new. I don't understand what you mean by "ridge." I didn't notice any ridge during the assembly either.

The piston had seized in cylinder 3, and the bearing shell was almost completely worn away.

I have the temperatures, of course. Everything was checked and found to be normal.

What's also noticeable is the smell. It's pungent, but there's no visible smoke. It smells like starting a diesel engine from 1980 when it's cold. Throughout the initial warm-up phase, it smells bad, even when it's no longer misfiring but is running smoothly.

Here are some videos of different starts. He only does it once, so you have to wait at least 6 hours before he does it again.

In the bores where the sealing elements are located, you'll usually find a slight ridge that you can feel with your fingernail or a small screwdriver. This ridge should be smoothed out so that the O-rings are not damaged in that area.
In the video, it looks like there are misfires. How about the compression? Did you replace the wiring harness for the PD elements, or did you slightly twist the connector plugs on the PD elements to achieve better contact?

The topic of "Grat" is understood. I haven't checked it. The question is, how likely is that? That would require completely redoing everything. I would like to check that immediately.

The PDE connectors are aligned as specified by VAG. The wiring harness in the control unit is new. I don't understand why a slight tilt of the PDE connectors would improve the contact, since the connectors have a locking mechanism. And if that were the case, why would it only happen during cold starts?

Wouldn't interruptions be logged as errors?

Instead of tilting the PDs, try angling the two contact tongues inside the connector. I always do it this way, and in most cases, it saves you from having to replace the entire wiring harness.

I don't know when it stores a fault code in the error memory, or how many times the fault needs to be detected before it's stored, and it seems to be minimal in your case.

If you're experiencing engine stalls due to fuel starvation ("cut-outs"), the O-rings might have been damaged. But it's just a guess.

If you're experiencing misfires, you might see white smoke coming from the exhaust.

Okay, understood.

I'm grateful for any advice, but I need to prioritize things based on probability and effort, so I can decide what to check next. The questions are not meant to be rude.

In my opinion, a loose connection is less likely. A dead battery, on the other hand, is more probable. That at least fits the pattern because he only does it once.

But if it only runs for a short time, like 10 seconds, and then stops vibrating, and I turn it off and on again, it starts vibrating again. If it's been running for 30 seconds, it doesn't vibrate anymore.

In short, I'll keep that in mind. The "Wackler" is out of the question for me, at least for now.

I replaced the wiring harness because the O-ring that goes on it wasn't available separately.

He doesn't smoke. However, it smells like cold diesel, as mentioned above. The BLS Golf V that I have also has a smell, but it's significantly less strong than the Audi. By the way, the smell lasts much longer than the engine misfire. You need to warm it up, but only while the coolant temperature is below 90°C; otherwise, it will start to smell.

Here are the PDE values.

I will first correct the angle and then check the compression.

The values are measured in the cold state, but after the vibration process has finished.

The high negative values in the MWB 23 would suggest a fuel shortage, but the tolerance range is +60 to -60.
Perhaps you can watch the first 10 seconds, but it will be almost impossible to do it within the given timeframe.

I'm experiencing a similar problem with my Golf IV AJM.
It only happens for me during the colder months. It also runs very unevenly for the first 5-10 seconds, and there's also white smoke.
Spark plugs and compression are fine. I haven't "dealt with" PD-O rings yet. I've also tried increasing the starting amount (more than what's possible with VCDS), but it didn't make a difference.
Perhaps it's also due to nozzle clogging.

Is it still just that one brief fluctuation in speed that you're experiencing?

I wouldn't change anything fundamental about the settings, as the car came off the production line with those settings, and we were probably working fine with them. Therefore, it is important to determine what is no longer considered a series.

Yes, I've noticed that too, but the tolerance that VCDS is reporting is +/- 100, not +/- 60. Where did you get the information that +/- 60 is the tolerance?

If the high negative values generally indicate a fuel shortage, how should the positive values be interpreted?
It doesn't make sense to me in terms of a logical cause-and-effect relationship.

The Difi is still old, and I think it might be replaceable, but probably not, because the car has always been regularly serviced.


No, it's really just the jerking during cold starts. Since it's known to need more diesel when running at full throttle, and it apparently gets it because it doesn't jerk at full throttle. I can't believe that idea.

Hi,

"The noises accompanying the cold start problems in the 'BLS 1.9 TDI - VID-20180109-WA0005.mp4' video, particularly during the engine speed drops, don't sound good." Does the engine run smoothly and properly even under full load?

Engine oil level remains the same and doesn't increase? To me, the noises sound almost like uncontrolled combustion due to dripping injectors/oil. Could it be...? Is the engine oil burning uncontrollably because too much of it is entering the intake manifold, and then slowly dripping into the combustion chambers when the engine is idling or stopped?

(Low oil level or Oil mist in the intake manifolds is normal due to the PCV system.

Coolant level is okay, and will it remain that way?

Best regards, Rainer.

Hi,

The coolant temperature has been stable for the past 250 out of 300 kilometers. Initially, it took something to get it going after the first fill, but in my opinion, that was just normal air.

Are 300 km not enough? Then I'll just drive a little further. Yes, I would say that it is running normally in the system.

I will check the oil level immediately and get back to you.

The video you're referring to. It's an older model, so it's possible that the faulty glow plugs are still inside.

I just checked the oil and coolant levels again, and they're fine. I also drove on a private road. Attached are some videos, maybe I'm already suffering from tunnel vision...

The cold start is now okay. It's not that cold right now, so it's not shaking as much, at least that's my feeling.

Hello.

Just set the correction angle to 0°; I've had quite a few experiences with strange behavior in these PD motors.
The effort required is very minimal, and you can probably rule it out.
Of course, the label file specifies the tolerance within which you are currently operating.
The software should also be able to compensate for certain deviations, but not all software versions have characteristic curves that are designed to be as tolerant as the tolerance specified in the label file.
My AMF (Automatic Motor Fire) in my Lupo doesn't start at all if the engine temperature exceeds 3.5°C. Have you tried it yet ?

"In Audi 8E vehicles with an AVF engine and Golf V vehicles with a BMM engine, I was able to eliminate this "rough running" after starting by adjusting the correction angle."

It's worth a try.

Regards, Mpire.