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Old 09-05-2007, 11:53 AM
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Join Date: Aug 2005
Posts: 20
Default Rough Idle...E430

Hello Forum

IHAC - My E430, seems to have a rough idle, the RPM gauge does show any surges, and when you press the pedal, it is a smooth climb -

I would be grateful if anyone can point me in the direction where I shoudl start looking??

Thanks in advance


2000 S430
2001 E430
2000 C240

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Old 09-05-2007, 02:48 PM
Join Date: May 2007
Posts: 1,057
Default RE: Rough Idle...E430

Check motor mounts,for leaks,wear,deterioration.Check plugs when was the last change?Run a can of injector cleaner thru the gas tank(techron)to clean the injectors.DO the above,if they dont clear it up.Post again and more measures will follow.
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Old 09-18-2007, 08:12 AM
Join Date: Sep 2007
Posts: 2
Default RE: Rough Idle...E430

I am having a similar problem with my 2000 E430 just happend 2 weeks ago thought it was bad gas but still doing it.Can you let me know how it works out?
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Old 10-04-2007, 07:36 AM
Join Date: Oct 2007
Location: IRVING,TX
Posts: 31
Default RE: Rough Idle...E430

I have a 2002 E320 that I bought usedw/71K miles 3 months agoand Ive been having the same problem of lately.It jerks a lil or a putting feeling when stopped at stoplights/signs and when taking off.Its been ideling weird unlike a Mercedes is supposed to(Drove2001 S430 & S500 of my parents).Im slowly but surely fixing the problem.I replaced my ignition coils(all 6) after finding out 1 of them went out and that helped the bad idel some.I replaced my fuel filter yesterday and that helped alot but hasnt fixed the problem completly, my check engine light is still on.Im getting all of this work done by a trusted mechanic of my family.The OBD code reads misfire in cylinder 1.My mechanic says after replacing the spark plugs time after time that the plugs in cylinder are coming out wet so he thinks its my fuel injector.I put a can of BG44k fuel system cleaner in before replacing the fuel filter and that instantly helped the acceleration.Reading similar posts, the mass air flow sensor may be my problem so I will probably buy 1 if my problem doesnt get any better in a week.Please reply when U figure out or fix your problem and likewise I will do the same now that Im registered on here
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Old 12-16-2008, 02:20 PM
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Join Date: Dec 2008
Posts: 6
Default RE: Rough Idle...E430

I had the same problem it seemed like it might be bad gas. Try taking the spark plug cover off and testing your 3 coil packs. You can hook a timing gun to the wires like I did or you can pull a coil pack out and if it makes no difference then that is your bad coil pack. Even running on 4 cylinders the @320 runs decent and shows symptoms similar to bad gas.
Mine runs fine now! Give it a try.
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Old 10-20-2009, 05:31 PM
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Join Date: Oct 2009
Posts: 3

The idle was also rough on my E430; it got over 100K miles. Lately, on very rare occasion, I got the check engine light on (P305, misfire on cylinder 5), the engine also hummed when I accelerated. The humming sound was similar to my Ford that had a bad air flow sensor. Anyway, this month, Pep Boys got the buy 1 Bosch spark plug, get 1 free after rebate so I bought some. I replaced all spark plugs on the E430, but the idle was still rough. By the advice from another forum, I removed the Mass Air Flow sensor with a special torx bit bought from Kragen to remove the 2 screws on the housing of the MAF. I sprayed the sensor with CRC MAF sensor cleaner bought from Kragen. On the sensor, there's a diode, and two air chambers with metal contacts inside them. Those needed to be spray-cleaned. I sprayed them all then let the whole sensor unit dry out (almost instantaenously because the chemical was very volatile). After I re-installed the MAF sensor, the humming is gone, the idle was much smoother.
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