BMW Repair Questions? Ask a Mechanic for Answers ASAP
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.
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.
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.
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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 replacementPlease 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.
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?
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.
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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?
Please can you reply to my last communication
Thank you in advance
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.
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.
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