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Steve
Steve, BMW Expert
Category: BMW
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I have an E46 318I and some times when it reaches temperature

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I have an E46 318I and some times when it reaches temperature it miss fires and some times stalls. No problems when cold or when running at normal up to speed temperature. Also does it when started form hot when it has been standing for about 30 mins.

What faults are being logged in the cars computer fault memory?
Customer: replied 5 years ago.

Steve


I have reset the codes and run the car until it stalled / misfired


The error code on shown was 170 Fuel Trim Malfunction (Bank 1)


On prior occasions had 153 & 141. Both Lambda sensors have been replaced. If you need ant further information please ask. Hope you have an answer for me.


Regards Chris

there are multiple things which can cause a fuel trim malfunction and rough running like this, as it is unfortunately a vague and generic fault

the most common based on what you have described would be a faulty temp sensor, intake air leak, failing crankcase ventilation system or possible fuel pressure issue (needs to be tested) or possibly even a clogged fuel or air filter. a bad airflow sensor could also be the cause

 

all will need to be checked.

 

Sorry if you were hoping for a different answer, please don't shoot the messenger - I can only give the honest answer, which I have. Please remember that a low rating PUNISHES me for my honest and prompt response, and I receive nothing for my time and answer until a positive rating is clicked.

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 for my answer, thank you. Best wishes with your vehicle.

Customer: replied 5 years ago.

Steve


thanks for the reply. As stated before I have no inlet leaks. Which temp sensor is it? Already checked the crank vent system. Not sure how to check the fuel pressure & have fitted a new filter. Should I fit a new petrol pump?

fuel pressure needs to be tested with an appropriate fuel pressure test guage. if pressure is off and the filter is new, a replacement pump should be fitted.

 

the temp sensor in the engine is the one in question, not the one in the radiator or coolant hose.

 

I am not sure how you checked for intake leaks but the only definitive test is a smoke test.

 

it would also be a good idea to invest in a scan on a high end BMW scanner which can monitor all live data and read more detailed fault codes. this small investment can save hundreds in wasted parts replacement

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 for my answer, thank you. Best wishes with your vehicle.

Customer: replied 5 years ago.

Hi Steve


Is me again


 


I have ordered a new fuel pump not to expensive as I have a trade account will fit it tomorrow. The car is 13 years old so its no done to bad.


 


As for the BMW program/tool I have it on my laptop and look at all kinds of data. Any particular thing I should be looking for?


 


Questions


How do you to do a smoke test


Why does it not play up when started from cold

you would want to look at the fuel trim readings and airflow readings. live data is great but it sort of needs to be used by somebody familiar with interpreting it and trained on it...

 

a smoke test requires a smoke machine which pumps smoke into the engine to look for it escaping from small cracks or holes

 

it doesn't play up from cold because it is either a temp related fault, something related t heat/expansion/tolerances, or is a bad input that the engine management system doesn't actually use during cold running.

 

Please kindly select a positive rating so that I receive credit for my time and answers, thank you in advance.

 

Steve and other BMW Specialists are ready to help you
Customer: replied 5 years ago.

Hi Steve


Fitted the new fuel pump and it is still playing up. Ran the program witlst running and fuel trim readings and airflow readings were all good


Also fitted an new MAF 10 months ago so cant see it being that


Not sure if this helps but when it is about to play up or stall the economy meter shoots to the top of the scale


 


Running out of ideas now and loosing patients with the car, its a shame as is is in mint condition!


 


Any idea of where I can take it for it to be tested, I live in South Wales


Also any idea how much it will cost?


Regards


Chris

Customer: replied 5 years ago.

Hi Steve


Please can you reply to my last communication


Thank you in advance


Chris

this is a difficult problem and apparently is not due to a common cause.

 

if you have not smoke tested the car warm, I would still consider that, and also a new temp sensor.

 

otherwise, a diagnostic on a factory BMW scan tool will be advisable as a next step. I do not know of any non dealers with this equipment in South Wales, unfortunately.

Customer: replied 5 years ago.

Hi Steve


Ok thank you


Have booked the in to my local BMW specialist on Saturday to put on the diagnostic. I will report back when I find out more.


Regards Chris

Customer: replied 5 years ago.

Steve


Good news the car is fixed


It was the MAF it was leaking air through the element & plug


The smoke test showed it up


Just thought you would like an update


Thank you for your help


Regards Chris