1997 BMW 540i Engine shakes like its missfiring when idling

Tiny
JLUCEY
  • MEMBER
  • 1997 BMW 540I
  • V8
  • 2WD
  • AUTOMATIC
  • 150,000 MILES
I am stumped, I am trying to figuere out why my 540i is running rough when it idles, it will sometimes do the same at highway speeds and the engine light will flash. Some people have told me I may have bad coils, bad intake seals, plugs and plug connectors, but I have replaced the spark plugs and 4 plug conectors and had the coils looked at and still idles bad, even checked out the intake seals and there still like new. I do however have a bad o2 sensor on bank 1, could that be the problem? It does go away after the engine light stop flashing, but the problem returns. HELP ME BEFORE I SELL THIS NICE CAR IF I CANT GET HELP!
Sunday, May 31st, 2009 AT 7:33 PM

9 Replies

Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Scan the computer for code/s

Engine misfiring can be caused by worn or fouled spark plugs, a weak spark (weak coil, bad spark plug wire), loss of compression, vacuum leaks, anything that causes an unusually lean fuel mixture (lean misfire), an EGR valve that is stuck open, dirty fuel injectors, low fuel pressure, or even bad fuel.
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Sunday, May 31st, 2009 AT 7:49 PM
Tiny
JLUCEY
  • MEMBER
  • 5 POSTS
The codes that came up were a bad o2 sensor and random misfire on cyl 1 3 5 7.
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Sunday, May 31st, 2009 AT 7:56 PM
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Random misfire normally caused by vacuum leaks and bad fuel.

Start checking the items I've mentioned earlier then comeback with some results
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Sunday, May 31st, 2009 AT 9:36 PM
Tiny
DOCHAGERTY
  • MECHANIC
  • 9,603 POSTS
A flashing check engine light usually indicates a misfire that is damaging to the catalytic converter and is usually caused by the coils, try swapping the coils from the left side to the right and see if the fault follows to that side, let me know what you find.
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Sunday, May 31st, 2009 AT 11:11 PM
Tiny
JLUCEY
  • MEMBER
  • 5 POSTS
Will do that and let you know soon
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Monday, June 1st, 2009 AT 1:49 AM
Tiny
JLUCEY
  • MEMBER
  • 5 POSTS
Changed the coils around now it reading missfire 1 2 3 4, very odd.
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Tuesday, June 2nd, 2009 AT 3:54 PM
Tiny
DOCHAGERTY
  • MECHANIC
  • 9,603 POSTS
Was there oil in the spark plug wells?
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Wednesday, June 3rd, 2009 AT 8:02 AM
Tiny
JLUCEY
  • MEMBER
  • 5 POSTS
Nope, they were very dry and clean.
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Wednesday, June 3rd, 2009 AT 11:51 AM
Tiny
DOCHAGERTY
  • MECHANIC
  • 9,603 POSTS
Has the DME ever been reflashed? Is there a round gray sticker on the "B" pillar that would indicate if there has been any dealer performed updates? Do you have the history of the car from it's warranty period?
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Wednesday, June 3rd, 2009 AT 2:32 PM

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