97 e 420 rough idle

1997 MERCEDES BENZ E420
200,000 MILES • V8 • 2WD • AUTOMATIC
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SEVENTHUNDERS
  • MEMBER
  • 1 POST
97 e420 runs and starts great but has rough idle always
Dec 12, 2010 at 1:47 AM
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RASMATAZ
  • CAR REPAIR CONTRIBUTOR
  • 75,992 POSTS
Engine running rough or misfiring can be cause by the following:

1.Defective spark plug.
2.Inadequate spark/coil,defective spark plug wire.
3.Lack of compression
4.Vacuum leak
5.Fautly fuel injectors.
6.Insufficient fuel pressure.
7.Contaminated fuel.
8.EGR valve that is leaking.
9.Oxygen sensors.
Dec 12, 2010 at 1:51 AM
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