BMW 120d experiences jerking/stuttering in specific RPM ranges.

Hello everyone,

I own a BMW 120d, first registered on 07.07.2007, 130kw, with 254,000 km so far. The brakes were replaced in 12/2015. An oil change was performed in March 2016, and I indicated that the car was running unevenly. Subsequently, read error codes, check diesel particulate filter, perform regeneration.
Exhaust manifold leaking, was was replaced in July 2016. The hissing sound didn't stop, and in July 2016 both timing chains were replaced, along with the clutch and all related seals. The car then passed the TÜV (German technical inspection) without any problems in July 2016. However, the problem worsened towards the end of July. According to the error code, the problem is likely the particulate filter. The car has received a newly installed particulate filter, and BMW has always regenerated it on the highway whenever the "Particulate filter full" warning light appeared.
Furthermore, I was told that the engine coolant gauge was broken, and that the sensor was malfunctioning, which caused the engine to overheat. I have the invoice for everything I have written here, except for the last item. Unfortunately, I don't have any measuring devices or even the slightest idea about it.
I've put so much money into this car, I don't want to sell it Can anyone help me? I live between Hildesheim and Hanover. The car has run perfectly all winter. As soon as the outside temperature rises above approximately 13 degrees Celsius, it starts to vibrate excessively between approximately 1800 and 2000 revolutions per minute, and sometimes even at the intersection while idling . I'm at a loss, and neither the mechanic nor I can figure out what's wrong.

Warm greetings, Josy

Hello.

Okay, generally speaking:
Without a diagnostic system, you cannot effectively troubleshoot, you need someone who can spend some time with you and their diagnostic equipment,
observe all parameters (relevant temperatures, pressures) and the DPF, to check if the target values are reached.

Getting to the point:
I had 3 BMW diesel cars (1x 320d, 2x 325d) this winter, all with the same problem and non-regenerating DPF.

In all three cases, the coolant thermostat and the EGR thermostat were defective. Since the change, all three are running and regenerating without any problems.
I mean both times the coolant level controllers, not the sensors/probes.
It is already sufficient if one of the two no longer functions correctly, the two temperatures that are to be controlled,
are used as a starting criterion for the regeneration of the DPF in the BMW control unit.
If the DPF's full loading condition is reached, the system typically attempts to reach the burn-out temperature of the DPF through multiple and after-injection.
However, if the engine and exhaust system remain cold, it won't work properly, and the DPF will fail.

The restless movement comes precisely from the fact that nothing is passing through.

Replace BOTH thermostats and don't let anyone dissuade you, replace both
- AGR Thermostat, BMW part number: 11717787870
- BMW coolant thermostat, part number 11517805811

The parts cost around €85 in the set from the original supplier.
Working time approx. 3.5 hours

Greetings, Mpire

Thank you, Mpire, for the quick response.
Exactly, I meant the coolant thermostat. Unfortunately, I can no longer determine whether only the sensor or the thermostat was replaced.
Then I will simply order the set that you mentioned and bring it to the workshop, telling them to replace it for me. The AGR thermostat was definitely not replaced, thanks for the tip.

Should I, in your opinion, instead seek someone out beforehand to accompany me on such a diagnostic trip? Maybe I'll find someone nearby who would do it with me, then I'll post the results here.

And did you simply replace the two thermostats and then it was okay, or do you need to pay attention to something afterwards, e.g., a long drive on the highway, so that the DPF regenerates again? What surprises me is that the car displayed a message last summer that the particulate filter was almost full, and this year there was no message. And, as I said, it only stutters/jerks/has issues when it's warmer than 13 degrees Celsius outside.

Thank you for your response.
Can I order the parts myself or only through a workshop? Are these the exact part numbers for my car, or should I pay attention to something else when ordering?

josy301 wrote:

Should I, in your opinion, rather seek someone out beforehand who can accompany me on such a diagnostic trip? Maybe I can find someone nearby who would do it with me, then I'll post the results here.

- If you have data from a diagnostic or troubleshooting trip, either BEFORE or AFTER the repair, you can see exactly what was wrong, and even whether your repairs were successful.

josy301 wrote:

And did you simply replace the two thermostats and then it was okay, or do you need to pay attention to something afterwards, e.g., a long drive on the highway, so that the DPF regenerates itself again?

- Ja, danach war alles wieder in Ordnung. Ich habe dann noch eine längere (50km) Fahrt im Teilbetrieb gemacht, wobei die Drehzahl zwischen ca. 130km/h und 2500U/min lag, und maximal 3000U/min. Es wurde nicht Vollgas gegeben. If the DPF is very full, it can get very hot.

josy301 wrote:

Can I order the parts myself or only through a workshop? Are these the exact part numbers for my car, or should I pay attention to something else when ordering?

- Of course, you can order/purchase the parts yourself.
The numbers are BMW part numbers, but you can also get the parts from BEHR, Gates, Hella, Valeo, etc.
BEHR is the original equipment supplier.
But it would be better to discuss this with your workshop beforehand, not all mechanics are willing to install parts brought in by customers and provide a warranty for them. Workshops also often get very good prices for replacement parts.

Greetings, Mpire