[paulie1201]

Hello i have recently bought a 2011 bmw f11 520d auto and once car is warm at operating temperature at low speeds the car seams to jerky and shudder while trying to maintain a set speed 30/40 mph its not nice feels awful any information on this matter would be a massive help as i really like the car but would like to get to the bottom of this issue

[RockCrusher]

Originally Posted by paulie1201

Hello i have recently bought a 2011 bmw f11 520d auto and once car is warm at operating temperature at low speeds the car seams to jerky and shudder while trying to maintain a set speed 30/40 mph its not nice feels awful any information on this matter would be a massive help as i really like the car but would like to get to the bottom of this issue

You bought the car used. How well do you know the car's service history?

First thing with a diesel I'd look into the fuel filter. I forget the fuel filter change schedule for my VW Golf TDi but not only was the filter scheduled to be changed but between filter R&R services there was a water drain that needed to be opened to drain any water from the filter housing water trap. I did this on schedule and at most got just a drop or two of water. But water trap (if fitted of course) draining and following the fuel filter replacement schedule are not things I'd let slide.

And on the subject of filters, consider the engine air filter. And the cabin air filter too, which of course plays no role in how the engine runs but does affect the heater/AC operation.

I'll add that one of the few times I had any engine issues with my VW Golf TDi was from a bad coolant temperature sensor that reported a higher than actual temperature to the engine controller. Cold starts were ok but the engine just didn't run quite right -- compared to how it ran before the temperature sensor started acting up -- after a cold start.

The other issue was at some point (approx. 150K miles) the glow plugs were replaced. My vague recollection is while the engine didn't manifest any untoward behavior before these were replaced after they were replaced engine starts were a bit better and the engine ran a bit better after the cold start. I saw the old glow plugs and they were clearly past their change by miles.

Another possible problem -- although over 6+ years and 150K miles I avoided -- was with at least the TDi engine the intake manifold could "coke" up from a combination of soot from the EGR system and water vapor from the crankcase ventilation system.

From the very outset of my ownership of the TDi, which I bought new, I took pains to avoid this condition and was successful. Just before putting the car up for sale I removed the air filter box and enough of the intake air piping to check the intake runners downstream of where the crankcase vent hose connected and the intake runner walls were dark with oily film but there was zero build up of any harder material.

Beyond the above there's the question about the operation of the low pressure fuel pump. But the high pressure fuel pump can also develop problems.

The MAF can also be suspect. It can provide the engine controller with the wrong intake air temperature or even fail to correctly measure air mass.

But the above possible issues are not something you can identify without some investigation/diagnosis.

If the CEL is not on there is no error code to help you. But there might be a pending error code which if present could shed some light on the cause of the behavior.

There could also be proprietary codes logged which can help identify the problem. These are available to a tech with access to a diagnostics computer. Aftermarket diagnostics scan tool might be able to retrieve these but I have no experience with any and can't make any recommendation.