E-Class (W124) 1984-1995: E 260, E 300, E 320, E 420, E 500 (Includes CE, T, TD models)

300e 2.8 idle problem

Old Mar 2, 2004 | 02:03 PM
  #1  
Z300E's Avatar
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From: Maryland
1993 300E 2.8
300e 2.8 idle problem

I have an intermittent idle problem. When I come to a stop, the idle fluctuates between ~500 to ~1200 rpm and then eventually stops. I have replaced the following: ECU, engine wiring harness, fuel pressure regulator, over voltage protection relay, plugs, fuel filter, air filter, O2 sensor. AND STILL this persists. Anybody out there have any idea how to fix this?
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Old Mar 2, 2004 | 03:13 PM
  #2  
Jer's Avatar
Jer
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From: Middlefield, CT
1994 E320
Seems like you've hit everything but the idle air control valve. Judging by the big fluctuations in idle speed, I reckon this is not a matter of leaky or worn-out injectors.
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Old Mar 2, 2004 | 08:22 PM
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Simple, but expensive,..
I had the exact same problem and it turned out to be the air mas flow sensor.
It ill cost you between 2 to 3 hundreds...
Mine is a '93 300E 2.8,.. how about yours?
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Old Mar 29, 2004 | 07:34 AM
  #4  
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From: monkeytown
Hey,

I think my car has the same problem 93 300E 3.2L w/93k Miles... when you start it and it's cold... it idles really loopy and once warmed up it'll idle around 550 and belch out black smoke and will stall out and just keeps doing it... Any Suggestions?

valT.
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Old Mar 30, 2004 | 03:34 AM
  #5  
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From: Reading, UK
C280
This is a common problem with the 280's and 320's

I would suggest that you clean out the throttle body. Inside the throttle body you have a butterfly flap that collects a load of crud on its outer edges. This stops the flap from closing properly and creates an air leak which in turn causes the revs to surge at idle.

Once you have cleaned the edges of the flap.....carb cleaner and a rag works well, you should find that the idle starts to settle down.

Do this before you contemplate changing you Mas meter, as you could save yourself a fortune!
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Old Mar 30, 2004 | 07:30 AM
  #6  
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From: monkeytown
Originally posted by mjtray
This is a common problem with the 280's and 320's

I would suggest that you clean out the throttle body. Inside the throttle body you have a butterfly flap that collects a load of crud on its outer edges. This stops the flap from closing properly and creates an air leak which in turn causes the revs to surge at idle.

Once you have cleaned the edges of the flap.....carb cleaner and a rag works well, you should find that the idle starts to settle down.

Do this before you contemplate changing you Mas meter, as you could save yourself a fortune!
Thanks, i'm gonna try that.

vnt
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Old Mar 30, 2004 | 09:43 AM
  #7  
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From: Germany
'00 S320 W220, '98 A160 W168/ sold in 2005 '86 260 E W124 '90 260E W124
have you checked the intrusion of extra air into the gas/air system, e.g. injector seals, air intake hoses, vacuum lines .... To check this spray brake clean of alcohol on the running engine and see if the spray has influence on the idle.
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Old Mar 30, 2004 | 09:45 AM
  #8  
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From: monkeytown
Originally posted by bamberger_1
have you checked the intrusion of extra air into the gas/air system, e.g. injector seals, air intake hoses, vacuum lines .... To check this spray brake clean of alcohol on the running engine and see if the spray has influence on the idle.
heck, i'll try that too.

vnt
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