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E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old 01-25-2013, 07:20 AM
Rueberger Rueberger is offline
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Location: Hermitage pa
 
Join Date: Jan 2013
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Mein Auto: 1999 528i
E39 rough idle when hot

So here goes, car has 160k on it and it threw a check engine light and started running rough. Pulled code for a misfire, changed all the plugs still run rough. Thought maybe the maf was bad cause when I unplugged it it didn't idle as bad and after driving around didn't seem to big down like it was only on 2 cylinders. I replaced the maf and soon as car was hot it did the same thing again. Going crazy with this
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  #2  
Old 01-25-2013, 08:07 AM
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johnstern johnstern is offline
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Location: Cape Neddick, Maine
 
Join Date: Mar 2007
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Mein Auto: 2000 BMW 528iT/5, S/C
The most likely problem is a vacuum leak. They are very difficult to find without a smoke test but one of the most frequent leaks are ones in the intake boots after the MAF and before the throttle body. It is necessary to remove these rubber boots to inspect as the tears/cracks are usually found in places you cannot see with the boots installed in the car.

The hose clamps for the boots that connect to the throttle body are a PITA and are best accessed from under the car unless you remove the driver's side cabin filter box and duct. Then you still need a 1/4 " drive 6mm swivel socket and a long extension to access.

Good luck
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Old 01-25-2013, 09:27 AM
Rueberger Rueberger is offline
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Location: Hermitage pa
 
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Mein Auto: 1999 528i
I get the vacuum leak thing at the idle but why would after the car warms up it gets worse and starts to shake when you give it gas? Would that leak cause it to load up on gas??
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Old 01-25-2013, 11:09 AM
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Ltmax Ltmax is offline
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Location: Jacksonville, FL
 
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Mein Auto: 07 750i, 02 540i Sport
I'd suspect you've got one or two coil packs going bad or the short plug wires under them. Recommend pulling the misfire codes again and they should point you in the right direction to find the one or two that need to be replaced. Don't need to replace them as a set.
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