# E83 X3 3.0d miss/stumble/surging idle - egr related



## Derangedrover (Feb 22, 2018)

Gday folks,

Looking for help with a problem with a new to me X3 3.0d.

At idle, particularly cold idle, engine has a miss/stumble/surge.
If revs are raised off idle, engine is smooth.
If I remove vacuum pipe from egr valve, idle is smooth. This sets MIL for insufficient egr flow.
Egr valve has been removed, cleaned and checked for function.
Can anyone tell me how the ecu receives feedback for egr flow, is it through the airflow meter?
What other sensors are involved in egr, ie egt etc?

Does amount of egr flow change if the cooler is in bypass or not? 

Any help or pointers to pertinent threads appreciated.

Cheers
D


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## Doug Huffman (Apr 25, 2015)

The precept here is to examine stored DTC error codes indicating symptoms, not failed components, as where to start on the fault tree for potential causes of that symptom.


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## Derangedrover (Feb 22, 2018)

Thanks Doug.

Best I can see, there are no fault codes stored, other than the one I generate when I remove the egr valve vacuum line.

Cheers
D


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## dzlbimmer (Jul 16, 2017)

possible that you are converting to a default map when creating the fault.


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## alacey (Mar 14, 2018)

Do these cars have intake throttle valves? I know my Cummins had one. It was right before the EGR valve on intake and helped create a vacuum to pull air through the EGR. It had to be disconnected if you deleted your Cummins and those that forgot had the same issues you are describing. I don't know much about these BMW diesels yet, but what you are describing sounds like the throttle valve opening and closing.


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## Derangedrover (Feb 22, 2018)

dzlbimmer said:


> possible that you are converting to a default map when creating the fault.


Not sure what your saying here?
Can you elaborate please.


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## Derangedrover (Feb 22, 2018)

alacey said:


> Do these cars have intake throttle valves? I know my Cummins had one. It was right before the EGR valve on intake and helped create a vacuum to pull air through the EGR. It had to be disconnected if you deleted your Cummins and those that forgot had the same issues you are describing. I don't know much about these BMW diesels yet, but what you are describing sounds like the throttle valve opening and closing.


It does have an anti shudder valve before the egr.
It has an external return spring on the shaft so the butterfly position can be seen externally, it's not moving when the idle miss is present.
When I 'delete' the egr valve by removing the vacuum line it idles properly, just sets a code for low egr flow.
When the egr is enabled it has the idle miss but no codes are present.

Cheers
D


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