I don't know what to do anymore, help! My TDI is acting up!!!

Hello fellow DIY enthusiasts,
First of all, thank you for all the helpful tips and troubleshooting advice I've received here in the forum. Absolutely fantastic!

Okay, now let's get to my problem!
The well-known problem with the TDI is that it's not running properly. I have been to Bosch several times, supposedly to see their specialists, and also to a VAG service center.
"I've been to several workshops, but no one can really help me. They just want to replace everything possible without testing anything." Just going with my gut feeling.
Okay, so the symptoms: loss of power! This manifests as poor throttle response, lack of flexibility in the higher gears. For example, I'm driving at 120 km/h in fifth gear and want to quickly accelerate to 150 km/h, but it doesn't respond immediately; it takes a long time to get into the higher gears. While it's trying to accelerate, the engine also sounds strange, almost like it wants to but can't. In the lower gears, it drives almost normally, but you always feel like it's missing the right amount of power. I bought the car, a 1995 Golf TDI with 90 horsepower, six months ago. After the purchase, it was discovered that the turbocharger control valve was defective. After.
"After the valve was replaced, the car ran like crazy. After 2 months (10,000 km), there was suddenly a jolt on the highway, and then it started running poorly. At the Bosch service, they supposedly determined that the mass airflow sensor (MAF) was defective. They replaced it, but the car didn't run any better afterward. After many discussions on the forum and working under the car, I discovered that the boost pressure valve was faulty again. Now there's a new one in, but it still doesn't run properly. It's better, but not like before. My next step was to go to a VAG specialist workshop (which I was hesitant to do), and they thoroughly checked the entire engine, meaning..." Compression (25:1), pump start (operational), etc. They were unable to test the nozzles because they do not have a suitable pressure gauge. No errors were found in the memory. Otherwise, everything is fine.
Okay, that's enough for now!

What could the problem be? Could it be the pump? The nozzles?

Sure, no problem!
Patrick.

Oh, so the car now has 136,000 km on it. Actually, my TDI is still relatively new.

reuselkopp wrote:

While he's trying to accelerate, the engine also sounds strange, as if it wants to, but can't. In the lower sections, he drives almost normally, but you always get the feeling that he's lacking the right amount of power!

Hi.

I only have a short amount of time.

The above seems to indicate a problem with the injection molding process.
It could be related to the NBF (Neutral Buoyancy Facility) or the pump.
The standard leak test barely or doesn't detect such faults (especially in the pump).

Do you have a way to log the start of the injection process during a trip?

A stuck EGR valve could also be the problem, but in that case, the soot emissions are usually increased at full load.

Addendum:
I'm assuming the standard maintenance items, like fuel filters, etc., are already taken care of.

Hi Ulf,
What is the NBF? Is that the start date for funding? Has it been reviewed? The only option would be to go back to the Bosch species and bother them again.
Regarding the black smoke, I mean that it occurs when I accelerate hard. When I look in the rearview mirror, I can see black-brown smoke coming out. Does it have to be a lot of smoke to indicate that the EGR valve isn't closing properly? But if it weren't closing properly, wouldn't that cause a loss of boost pressure? Or not? How can I check if the EGR valve is closing properly?
Of course, I completed the mandatory tasks. The filter has been replaced twice, and even the preheating valve. Without success!

Best regards, Patrick.

Hi,
Okay, it's me again. Are you referring to the needle lift valve (NLV) when you say "NBF"? I've already done the test for the needle lift valve, but I didn't hear any misfires. Also, while driving, I noticed that the car gently jerks (stutters) when I accelerate, which would again suggest a faulty needle lift valve. Or would the car then really be unstable?

Best regards, Patrick.

reuselkopp wrote:

Okay, it's me again. Are you referring to the needle lift valve (NLV) when you say "NBF"? I've already done the test for the needle lift valve, but I didn't hear any misfires. Also, while driving, I noticed that the car gently jerks (stutters) when I accelerate, which would again suggest a faulty needle lift valve. Or would the car then really

struggle?

Hi.

Yes, NBF and NHG are the same thing.

Slight jerking can sometimes be caused by the fuel injector.

Visible soot, which can be seen in the rearview mirror during daylight without any modifications, likely indicates an issue with the EGR valve, in my opinion.
To check this, you need to open the intake path on the manifold and inspect the movement of the valve stem. If necessary, use pliers or a similar tool to loosen it.
Unfortunately, I don't know the details of the story regarding the 90 horsepower model.

Hi!

Simply slide a hose onto the EGR valve and suck on it firmly, while using a flashlight to check if the valve opens. After suddenly releasing the vacuum, the valve should close with a click. If it doesn't, replace it, or better yet, disable the EGR system -> see the article on exhaust gas recirculation. In my case, the EGR valve caused a 3 to 5 mm thick layer of soot and oil in the intake manifold and cylinder head (at 174,000 km 1Z), which restricts airflow. Cleaning can only be done by removing the cylinder head. However, it is possible to proactively replace the engine oil (I know someone who changes their engine oil every 90,000 km).

Best regards, Christian.

Hi!
My TDI exhibited similar symptoms. Ultimately, the wastegate valve (AGR) was replaced because the diaphragm had a tear.

Hi,

Mathias wrote:

Ultimately, the wastegate valve (AGR) was replaced because the diaphragm had a crack.

"Sorry, don't you think that's a bit of nonsense?"
Exhaust gas recirculation (EGR) and the wastegate are unrelated.

Best regards, Rainer.

Rainer K. wrote:

Exhaust gas recirculation (EGR) and the wastegate have nothing to do with each other.

However, both have a membrane-actuated mechanism.

*ouch* don't hit *ouch ouch*

[Translating...]

Hi everyone,
It's really great how things are progressing here!
Okay, I've already tried the test of attaching a hose to the AGR valve and using a vacuum pump, but it didn't really work. I couldn't create enough suction with my mouth.
With the engine running, the EGR valve opens, at least that's what it appears to do (the diaphragm moves). It closes again at approximately 3000 RPM. I don't know what sounds it makes when it does that. Why is it so important whether or not it makes an audible clicking sound? Can you...?
Then are they saying it's 100% certain?
I'll try installing that metal piece this weekend.
At what RPM should the EGR valve open and close?
Here's what else comes to mind regarding the soot: when I rev the engine while it's stationary, a lot of black smoke comes out of the exhaust, and directly underneath, there's a large black stain. I always thought a little bit of soot was normal for a diesel engine.

Best regards, Patrick.

reuselkopp wrote:

Okay, I've already tried the test of attaching a hose to the AGR valve and using a vacuum pump, but it didn't really work. I couldn't create enough suction with my mouth.

Hi.

No wonder, the can needs a significant vacuum pressure. Get a large syringe (ideally around 50 ml), it will work better that way.

Quote:

At what RPM should the EGR valve open and close?

It can't be stated that simply, as it also depends on the engine load/boost pressure and is controlled by a complex map.

Quote:

What else comes to mind regarding the Russians is that when I give it full throttle while stationary, a lot of black smoke comes out of the exhaust, and directly underneath is a large black spot. I always thought that a little bit of soot was normal for a diesel engine.

That's probably quite serious... either it's an EGR problem again, or there are leaks in the charge air pipes. They usually reveal themselves through hissing noises, especially under full load at around 2000 rpm.

Ultimately, the wastegate valve (AGR) was replaced because the diaphragm had a crack.
'Sorry, don't you think that's a bit of nonsense?'
Exhaust gas recirculation (EGR) and the wastegate are unrelated.

Greetings, Rainer

It smells strikingly!
Sorry, I was a bit confused. While the wastegate also regulates exhaust gases, the AGR system has nothing to do with it. However, I would still have the wastegate function checked, as the power loss disappeared after I replaced it.

Hi,
The actual wastegate is located inside the turbocharger and cannot usually be replaced. Do you mean the electric control valve?

Best regards, Rudi.

ulf wrote:

No wonder, the can needs a significant vacuum pressure. Get a large syringe (ideally around 50 ml), it will work better that way.

Hi Ulf!

Okay, I tried it with a hose on three 1Z engines (one even had a new EGR valve), and I didn't have any problems getting the hose to the valve. So, maybe it's difficult to operate and doesn't close properly???

Best regards, Christian.

haehnlein wrote:

So, I tried this with 3 1Z engines using a hose (one even had a new EGR valve)->no problems getting the hose to the valve. So, maybe it's difficult to operate and doesn't close properly???

Hi Christian,

Hmm... I can't get the EGR valve open with my mouth.
Perhaps the dosages differ for the various engines .

If the weight of one engine's casing is noticeably heavier than that of another, identical and apparently intact engine, there might be something wrong with the former - unless production changes were implemented specifically at that point.

Stubborn or stiff cans often reveal themselves by the fact that the movement cannot be controlled with precision.
Instead, the movement lags behind the pressure change, and/or it "jumps" when certain pressure thresholds are exceeded or undershot.