ruff idle - Mercedes-Benz Forum

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post #1 of 5 (permalink) Old 08-10-2004, 09:31 PM Thread Starter
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ruff idle

I own a 1988 420 sel with 115,000 mi,its beautiful, everthing works ,great body ect.. just filled up with high-test started running & ideling ruff. might be bad gas?? ran it down to half tank filled with sunoco 94 and fuel line/jet cleaner. still runs ruff.. all visibal vacum lines seem ok pushed down on all plug wires.. could it be plugs>> what do you think?? please advise .. thanks T
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post #2 of 5 (permalink) Old 08-10-2004, 11:33 PM
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RE: ruff idle


I'm assuming you ran some sort of fuel injector cleaner. If this is so, then all the gunk inside the engine might have clogged up the fuel filters. Clogged fuel filters will cause less fuel to be pumped into the engine, hence the rough idle.

I'd look into replacing those fuel filters first.


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post #3 of 5 (permalink) Old 09-20-2004, 07:58 PM Thread Starter
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RE: ruff idle

thanks much did all that changed plugs, wires, rotor, now i am told i need a fuel dist head.. can anyone help in locating one for less than the $2400.00 !!!!! that the dealer wants.. ?? help ..thanks tony i
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post #4 of 5 (permalink) Old 09-21-2004, 06:43 AM
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RE: ruff idle

Hi Tony,

See German Star, a BenzWorld supporter, for your needs. Good quality parts & especially service. Below is the link for your fuel system parts. I think you will be pleased.

Cheers, MBL
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post #5 of 5 (permalink) Old 09-21-2004, 10:17 PM
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RE: ruff idle

Welcome to the forum and the world of rough/high idle in the w126. Here are some things to check:

1. Idle control valve
2. Idle control unit
3. OVP relay
4. Throttle position switch
5. Worn injectors
6. Broken/brittle/missing/disconnected vacuum hose(s)

From your description number 4 may be a good place to start:

Post in the w126 forum from now on – lots of very experience folks there to help because we have the best MBs ever made.
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