Clogged Diesel Filter: Symptoms and Causes

Hey fellow mechanics,

This morning, I had the following problem: The outside temperature was -10°C, and I had filled the tank the previous evening. The engine started well. After driving about 3 kilometers through the village without any problems, I got onto the country road, and the car suddenly started hesitating and not responding properly to the accelerator. Then, the ASR/ESP warning light in the cockpit started flashing. I thought, 'Hmm, is it icy?' It felt like driving on ice, and I couldn't give it any gas because the ESP system was detecting wheel spin.
Then, suddenly, the ESP light started to stay on continuously. However, the road was not slippery, but dry.
My TDI was now only reaching speeds of 50-60 km/h even with the accelerator pedal fully pressed, and it was sluggish.
I immediately drove to my mechanic's shop. Even when the car was stationary, the ESP light was still illuminated.
Then, the ESP control unit's memory was read. It displayed 'Error detected, please read the engine control unit.'
The error code 'Intermittent fuel injection timing - control difference' was registered in the engine control unit.
However, the preheating light did not flash.

The ultimate cause was a clogged or frozen diesel filter. 'This happens from time to time,' the mechanic said, 'because there's always some water mixed in with the diesel.'

I personally suspected a faulty wheel speed sensor. But it usually turns out to be something different than you expect...

Regards,

Eike.

eike wrote:

Then, the ESP control unit's memory was read. It displayed "Error detected, please read the engine control unit." The error code "Intermittent fuel injection timing - control difference" was registered in the engine control unit. However, the preheating light did not flash. The cause was ultimately a clogged or frozen diesel filter. "This happens from time to time, as there is always some water in the diesel," the mechanic said.

Hi Eike,

That could even all be true [Sarcasm ON] even though the information came from a workshop [Sarcasm OUT].

The injection start adjustment works based on the internal pressure of the pumps, and to build and maintain this pressure, a free injection flow is required.
By the way, there is also a free fuel flow, so that the pressure does not rise too high.

I can verify the issue with the warning light.

While using a 10-cent tuning, I experienced a few instances where the car went into limp mode. In those situations, the ASR light illuminates, and the ABS display shows 'Please read engine data.'
It also reports a 'quantity setting device regulation difference.'

If I activate the 'hardcore' 10-cent mode from the start, the heating element starts blinking.

very mysterious approach...

CU Gremlin.

Hello Ulf,

ulf wrote:

By the way, there's also a free flow of fuelto prevent the pressure from getting too high. IMHO, there's a pressure relief valve in the pump, so it wouldn't do anything. The fuel would just be circulated. Best regards, Rainer.

Rainer K. wrote:

Hello Ulf, ulf wrote: By the way, there's also a free flow of fuelto prevent the pressure from getting too high. IMHO, there is a pressure relief valve in the pump, so it wouldn't do anything. The fuel would just be circulated within the loop. Hi Rainer, According to my yellow Bosch manual on VPs, the pressure control valve (which controls the in-circuit pumping) and the overflow throttle (in the return outlet) are matched to maintain the pump's internal pressure at the intended speed-dependent level. Therefore, the return pressure should also have an influence on the injection adjustment. . .

:

Hello Ulf,

I think the hole in the return screw shouldn't be too large, otherwise the necessary internal pump pressure might not be achievable.
The pressure regulating valve itself should be a standard pressure relief valve.
That's just my current understanding, and it doesn't necessarily mean it's correct.

Best regards, Rainer.