Golf 4 ALH Misfire: Causes & Fixes

Hello!

Here's a Volkswagen Golf 4 with the ALH engine, 130,000 km, manufactured in 1999. It was experiencing a lack of power, and the Mass Air Flow Sensor (MAF sensor) from Bosch was replaced.

According to the customer, the service is now okay, but he is experiencing engine misfires at idle, and the car is stalling while driving. Additionally, the intake noise at full throttle doesn't sound as it should.

Initially, this jerking was only noticeable in the lower RPM range when accelerating from idle to full throttle.

When I disconnect the LMM (mass airflow sensor), the engine seems to run a little smoother. (The AGR valve is also new.)

Which logs would be useful?

Quote:

The mass airflow sensor (Bosch) was replaced.

Which brand is it being replaced with?

Bosch replacement part.

I usually get 8, 10, or 11 hours of sleep.

I've experienced similar jolts before -- the new LMM is defective.

I would (before any extensive troubleshooting takes place) try to switch the LMM again, if possible, or replace it with a known good one, in order to be able to definitively rule it out as a source of the problem. The fact that the vehicle didn't exhibit any issues before could be an indication of a faulty new part, as I mentioned - it could be .

What are the basic parameters: ignition timing, valve timing, fuel injection start/fuel injection control, etc.?

Hmm, yes, I'll order another one.

LLRR is not yet possible in this system, as far as I remember.

According to the TDI timing, it's in the upper range but still okay.

The KR filter is also new.

According to the documents, the water pump was replaced at 90,000 km, but I haven't checked the timing yet.

I spoke with him again just now.
The engine is idling roughly, and when the RPM reaches 900, it occasionally drops to 800 RPM for a few seconds.

While driving in the lower RPM range (2nd, 3rd, and 4th gear) between 1500 and 2000 RPM, with the accelerator pedal held steady, a jerking or stuttering sensation can be felt at regular intervals.

Dept. 038 906 012 FA 3349

Is there possibly an update for this?

Quote:

I haven't checked the valve timing yet.

You can save money if the pump fits.

You can try the old LMM again. If it still provides reasonably good readings at lower RPMs and the vehicle doesn't jerk, ...
However, a constant replacement value (often 550mg/H and a fault memory entry) should have been displayed for the air mass, which makes testing with the old part less meaningful.

The problem was actually with the mass airflow sensor (MAF), and everything works fine with the new one.

Thank you for the feedback!

Finally, one more question:

Was was the origin of that Bosch replacement part: was it a new part purchased from a specialized retailer, or was it bought from an online marketplace like eBay?

Background: There may be instances of plagiarism circulating – because, in fact, this exact error occurs in the copies.

You can be seriously harmed by this error if it doesn't occur immediately after replacing the mass airflow sensor.