Low Smoke Suppression: Causes & Solutions

'I'm experiencing power loss in my Passat, model year 1994 (1Z TDI). It's not pulling very well overall. I've already read the diagnostic trouble codes.'
In group 8, the smoke reduction is controlled by torque limitation. I have already replaced the mass airflow sensor (MAF) because I cleaned it and it got damaged, so I had to buy a new one. The smoke reduction values are mostly between 15 and 25 mg/H, but occasionally I see values up to 38 mg/H.

Where should I look for the error next?

What air mass value does the new mass airflow sensor show at 3000 RPM and full load?

I took the values from group 3.
at 4347 RPM - should be 841, is 681, and...
at 3024 RPM - should be 847, but is 814 and 625.

At 3000 RPM, I have two different values in my tables.

I took the values from group 3.
at 4347 RPM - should be 841, is 681, and...
at 3024 RPM - the expected value is 847, but I have 814 and 625 here... I have two different values in my tables...

Hello,

Either your mass airflow sensor is faulty, the valve timing is incorrect, or the exhaust system is blocked (e.g., the catalytic converter is dissolved, a pipe is kinked or detached). It's also possible that your boost pressure is too low due to a fault, and the low air mass is a consequence of that.

Best regards, Rainer.

Hi,

I would like to join in here as well.

Hopefully, this is okay. Regarding thread hijacking.

I'm experiencing the same problem with a 1996 AFN automatic.

The smoke suppression is too low, the boost pressure is correct in all situations, but the target mass airflow value is also a bit too low.

LMM is new (values have improved slightly, but are still too low).

I have checked the AGR valve, and everything is okay. The mass airflow sensor (MAF) is an original part. I haven't installed anything anywhere.
I need to check Kat.

I haven't adjusted the timing, and the timing belt is tight.

Could it also be coming from the fuel injection pump or the electric valves?
I loosened the ESP (Electronic Stability Program) because of an incorrect injection timing and then adjusted it correctly.

But since then, it hasn't been running well at high speeds; it makes a ticking sound when warm (at idle) and can't reach its top speed anymore.

I'm not sure about the error, but could adjusting the ESP too much potentially shift the valve timing by a tooth?

Low air mass can also be caused by an EGR valve that is not closing properly.
(to test, place a piece of metal in between).

Best regards, Micha.

I already tried that with a metal sheet, but it hardly made any difference.

I'm afraid it might be related to the ESP (Electronic Stability Program) or the valve timing.

I will check the valve timing, unless you think it's impossible for it to be affected when adjusting the ESP.

I'm not sure how to check the ESP (Electronic Stability Program).

Quote:

I'm afraid it's in the area of ESP or valve timing.

No. Lack of boost pressure or blockage...

I'm afraid it's related to the ESP or the valve timing.
No. Lack of boost pressure or blockage...

Hi,

The boost pressure always matches the target values. As I said, the problem started after I tried to adjust the ESP. Therefore, I suspect the error is related to the ESP or the valve timing. What do you think?

I'll check for constipation. However, since the problem started after I began taking the medication, it seems like a big coincidence if something else is broken.

'Also, another thing is that it's idling a bit rough when it's warm, which wasn't the case before.'

But thank you for the tips, everyone. I think this forum is really great.

I will be doing the following next week.

Check the valve timing (this can help rule it out).
Test the exhaust and catalytic converter for blockages (how exactly? by tapping?).
Check charge pressure hoses.

After that, I'm also at a loss.

According to the measurement data, the air mass is too low, and the smoke limit is also too low, while all other values are very good.