Hello every body , my car ( e38 1997 740 eur ) has poor fuel economy with moderate driving . city 4 km / l , highway 6.5 km /l
no errors except for map cooling , bank 2 o2 sensor .
maf , injectors , plugs purge valve , fuel filter , fuel pump and engine gasket are replaced with no change
I have rough cold start with low power but its fine when get hot . only fine roughness at idle and sometimes tiny hiccup at rpm 2k when car in parked otherwise the acceleration is very good . I upload some pic from inpa , smoothness is shown to irregular I switch off the coils and no change .
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Last edited by haydar alameen; 11-11-2018 at 05:00 PM.
A bad thermostat and upstream o2 sensors can lead to bad MPG. Bad intake gaskets can also potentially cause false o2 errors from the additional air it is pulling in before the engine gets hot and expands the gasket a bit. I had a bad cold start idle and an intake reseal resolved that. All new intake gaskets and TB gasket. Might consider doing the valley pan while the intake is out too...
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Your adaptation values do not support an O2 error - unless you have cleared adaptions just before you took the screenshots, or, the O2 sensor is dead. What was the O2 error?
Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i
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Last edited by haydar alameen; 11-11-2018 at 11:57 PM.
I would guess then that the O2 error was not an 'adaptations at limits' and is a real O2 error. In which case, as purplecty says - you won't get good MPG until that problem is fixed by replacement of the Lambda sensor...
Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i
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All explained here:
Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i
My BMW Repair YouTube Channel
My Current 840ci Sport Individual
My Current 650ci Sport Individual
My E31 Repair and Information Website
My E38 Repair and Information Website
My E63/E64 Repair and Information Website
Chase - Heroes to a generation
Here is the gasket
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Replace all of them even the ones on the front and rear and the throttle body one as well...
https://www.fcpeuro.com/products/bmw...et-11611433328
https://www.fcpeuro.com/products/bmw...et-11611729728
https://www.fcpeuro.com/products/bmw...or-11611729727
https://www.fcpeuro.com/products/bmw...et-13547510433
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Last edited by purplecty; 11-12-2018 at 02:43 PM.
Any luck?
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Update , It was the manifold gasket which cause poor power and rough idle , economy is still and I will give you feedback
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Why universal o2s? The direct fit bosch ones are cheaper and plug and play...
https://rover.ebay.com/rover/0/0/0?m...2F252282318699
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Last edited by purplecty; 11-16-2018 at 05:38 PM.
Thank you Timm
I saw your videos previously , its simple and very informative .
Regard the o2 sensors it should be oscillating on inpa or not , I use the reading of l/ h from test 4 and I see there is no correlation with voltage changes of the sensors in inpa !
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When the engine is at running temperature the pre-cat O2 sensors should be swinging around the scale - the O2 sensors are narrow-band devices and can only detect if the mixture is too lean or too rich (unlike wide-band O2 sensors which provide a linear reading of oxygen levels).
The DME is constantly adjusting the fuel/air mixture - it increases the fuel when the O2 sensor shows the mixture is too lean and reduces it when it detects the mixture is too rich - it does this constantly so the O2 voltage swings around. The adjustments are quite small - but the O2 sensors are very sensitive.
The integrated Lambda reading is the filtered and integrated Lambda reading and gives a true reading of the average fuel/air mixture - it is that value that is worth watching - all explained here:
https://www.meeknet.co.uk/E38/Diagnostics.htm
Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i
My BMW Repair YouTube Channel
My Current 840ci Sport Individual
My Current 650ci Sport Individual
My E31 Repair and Information Website
My E38 Repair and Information Website
My E63/E64 Repair and Information Website
Chase - Heroes to a generation
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