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Steve, BMW Expert
Category: BMW
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Experience:  BMW Expert
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I've got a 2005 E66 with 170000 miles on the clock. It has

I've got a 2005 E66... Show More
I've got a 2005 E66 with 170000 miles on the clock.
It has recently started using between 10 and 20% less fuel.
The engine runs fine but there can be steam (smoke?) rising up the sides of the car in the vicinity of the front doors when I stop, plus a strong smell of fuel.
A local diesel expert reckons it is not the DPF but, perhaps, one or more exhaust sensors.
Nothing comes up on a diagnostic check.
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What kind of diagnostic was carried out?
Customer reply replied 3 years ago.

I've had my BMW specialist do a check using, I presume, all the latest BMW stuff. He couldn't find anything.

the most recent test was using Bosch diagnostic equipment, I think. Apparently it is pretty good generally, but will not cover the sensors. Does that sound right?

I will provide an honest answer. I trust this will be appreciated. Please remember that a low rating PUNISHES me honest and that I receive nothing time until a positive rating is clicked.
If smoke is rising it is likely a leak or exhaust blockage, not a bad sensor. Sensor readings can be monitored with proper bmw equipment so if such a diag has not been run, I would suggest you invest in one.
Please let me know if you have further questions. Please do not forget to click a positive rating as this is the only way I receive credit answer, thank you. Best wishes with your vehicle.
Customer reply replied 3 years ago.

The rising 'smoke' looks more like steam (although it is not water vapour) and it does not occur all the time. As far as I am aware there is no leak or blockage in the exhaust.

As always the symptoms do not occur when the diagnostic test is being carried out.

Please do not forget to click on a positive rating
You are going to need to replicate the issue when diagnostics can be carried out if you hope to avoid guess work. The car should be raised so the source of the smoke can be found. There are many fluids than could leak and evaporate, or possible leak points. If the source of the smoke has not been identified it is hard to eliminate an exchaust leak or blockage fully.
Please do not forget to click on a positive rating