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2004 bmw 525i please help

5824 Views 11 Replies 4 Participants Last post by  AlexatosJR
Hi i was wondering if anyone has any information that could help me out. please and thank you
its a 2004 bmw 525i manual transmission with 84000, i just bought it from a dealership bout 6 months ago.

the other day i was at a red light and my service engine soon light came on as well as the high emission alert. that was my car started to rumble, but when i step on the clutch the rumble goes away. when i drive the car it drives perfectly normal its just when it come to an idle the car begins to rumble as if it was bout to die. it idles a little above 500 rpm but when i step on the clutch it idle around 6 or 7 hundred rpm

i changed the spark plugs to the bosch platinum +4 and the problem got worst, so i went to exchange the spark plugs for some ngk iridiums and it got better but the car still shook at an idle. when i took out the bosch platinums the tips were brown look like it was burnt

i took my car to a mechanic and he ran the the test. it said my car was misfiring almost all the cylinders and fuel was running too lean.

does anyone have an idea what it could be,
1 - 12 of 12 Posts
Try cleaning the mass airflow controller.
yeah i bought some maf cleaner. and clean the mass air flow sensor and there was no difference
Did you get it scanned? Codes? Coils bad?
While I was gettin it scanned the mechanic told me to change my spark plugs.to o some iridium cause the bosch platinum were ****n then come back. I saw some codes that said my cylinders were miss firing and my fuel wad too lean, I am going back to the mechanic tomorrow to get another scan
yeah codes were 171 and 174 fuel mixture too lean
You said you already cleaned the MAF sensor? Did you reinstall it with the gasket? Assuming you did, inspect your intake duct after the MAF sensor for crack or hole or anything that would cause your MAF sensor to report incorrectly to the DME. Some people had issues with cracked intake tube elbow which caused the same P0171 and P0174 mixture too lean codes like yours. Here's a DIY that you can look at. http://www.bmw330ci.net/maintenance/tubeelbow.php

Remember the I-6 M54 engine is configured similarly, just different piping for the MY application. You can also search this forum for "intake tube elbow" or "P0171" or "P0174" or "lean mixture". Everything you need is here...

Edit: The reason you have lean mixture is that your MAF sensor is giving your DME a signal that it is sensing only X amount of air passing through the intake. The DME adjusts fuel delivery equivalent to the amount of air for optimum scheduled mixture at a given condition. Little does the DME know that the MAF sensor is not telling you the truth because the engine is actually sucking in a lot more unreported airflow through the crack or hole in the intake. So now you have more airflow than fuel for optimum mixture - lean condition. I hope that explains it for you. Pretty simple...

At idle it is a big deal but at higher throttle setting the leak through the hole or crack becomes fractionally irrelevant, which is why you have semi good running engine when you step on the gas.

Here's where you normally find the crack(s) on the tube elbow - on the expansion folds:

http://www.flickr.com/photos/[email protected]/4913599390/
Hey! I just ran into this exact same problem a few days ago. I have been working through all the threads here about this problem. I have tried draining some oil, cleaning the MAF sensor and was working on getting the boots off when I found something else that fixed my problem. I decided to remove this large box (DISA Valve) on the intake to get to the hose clamps on the boot when I discovered it was broken. Made a temporary fix to see what happens and voila rough idle gone.

DISA Valve




Temporary fix:


I have ordered a new one from www.bavauto.com

Part Number:11 61 7 544 806

I have three pages of notes from where I have been working on this issue, feel free to ask any questions.
I do not know how safe this fix is and don't recommend it because if something breaks you will lose parts into the intake (vary BAD!) I am going to risk it untill my new part gets here but if you try it, you try it at your own risk.
Let us know how it works for you...
My temporary fix has worked great; I took the car out for a drive (a few good high RPM accelerations). Got back pulled the DISA back out and watched it switch back and forth a few times. I still don't feel confident that this thing will stay together so I still intend to get a new one. I'll update back when I get the new one installed.
Thank you for putting where you got the part and part number, very helpful even though this was posted a while back :thumbup:

Hey! I just ran into this exact same problem a few days ago. I have been working through all the threads here about this problem. I have tried draining some oil, cleaning the MAF sensor and was working on getting the boots off when I found something else that fixed my problem. I decided to remove this large box (DISA Valve) on the intake to get to the hose clamps on the boot when I discovered it was broken. Made a temporary fix to see what happens and voila rough idle gone.

DISA Valve




Temporary fix:


I have ordered a new one from www.bavauto.com

Part Number:11 61 7 544 806

I have three pages of notes from where I have been working on this issue, feel free to ask any questions.
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