RPM FLUCTUATION.
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Joined: Feb 2010
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00 S430 & 02 Suzuki 750 Katana
RPM FLUCTUATION.
Hey guys, I was wondering why sometimes when I am either at a stop light, or sign my RPM starts to fluctuate and make's the car idle a little funny like it seems like its wants to cut off then it doesn't. <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p>
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Like it’s not really that bad but I am concerned. My 2 sense tells me it could be either the motor mount going bad, or the catalytic converter is clogged up which could reverse the emission back to the engine. <o:p></o:p>
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Some guidance.. cuz I really love my e420 and I don’t want it to give up!!<o:p></o:p>
<o:p></o:p>
Like it’s not really that bad but I am concerned. My 2 sense tells me it could be either the motor mount going bad, or the catalytic converter is clogged up which could reverse the emission back to the engine. <o:p></o:p>
<o:p></o:p>
Some guidance.. cuz I really love my e420 and I don’t want it to give up!!<o:p></o:p>
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Joined: Oct 2007
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From: SoCal
98 Brilliant Silver E320 Wagon
I'm pretty sure you can rule out MM. That generally produces vibration especially when stopped and in gear. No effect on rpms.
You might start by scanning the car for OBD II codes. You can get a fairly inexpensive scanner at Harbor Freight. Follow the directions and write down the codes which have the form P0xxx where xxx is a 3 digit number. Next clear all the codes with the scanner (some maybe just transient). Go thru a few drive cycles over about a week. Now reread the codes. Post them here for help with interpretation.
Good luck.
You might start by scanning the car for OBD II codes. You can get a fairly inexpensive scanner at Harbor Freight. Follow the directions and write down the codes which have the form P0xxx where xxx is a 3 digit number. Next clear all the codes with the scanner (some maybe just transient). Go thru a few drive cycles over about a week. Now reread the codes. Post them here for help with interpretation.
Good luck.
Junior Member
Joined: Nov 2008
Posts: 39
Likes: 2
2015 SL400 and 2004 SL500
E420 Idle
That engine does idle at a low speed. My E420 idles at a bit over 500 rpm in gear. It did what you describe when the rear O2 sensors failed. A plug change and rear O2 sensors fixed it. Idle steady now. Also check your MAF/ throttle plate and clean it with some gumout spray.
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Joined: Apr 2007
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300E a couple 1994 w124wagon E320 Wagon/,1971MGB Track/Rally, MG Midget Autocross ,2000 E320 wagon.
Never use Gumout
On a MASS air sensor MAF is not part of the throttle plate/
use CRC mass air sensor cleaner.
use CRC mass air sensor cleaner.
Thread Starter
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00 S430 & 02 Suzuki 750 Katana
Well I recently got my spark plugs changed, fuel pump replaced and fuel filter changed as well <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p>
After I drove more than 200 miles was when I noticed the RPM fluctuating... <o:p></o:p>
The guys at the shop gave me an injector cleaner and fuel line cleaner they believed that since I drove all those miles it may have clogged the fuel lines a little.<o:p></o:p>
Long story short it doesn't fluctuate but I am still going to clean the MAF to be on the safe side as well. After this my next task will be... (the one and only CATALYTIC CONVERTOR drama) dun... dun.. dun... <o:p></o:p>
After I drove more than 200 miles was when I noticed the RPM fluctuating... <o:p></o:p>
The guys at the shop gave me an injector cleaner and fuel line cleaner they believed that since I drove all those miles it may have clogged the fuel lines a little.<o:p></o:p>
Long story short it doesn't fluctuate but I am still going to clean the MAF to be on the safe side as well. After this my next task will be... (the one and only CATALYTIC CONVERTOR drama) dun... dun.. dun... <o:p></o:p>
Thread Starter
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00 S430 & 02 Suzuki 750 Katana
Acts like its going to stall
Alright.. I cleanded the MAF and changed the CATS still acts like its wants to stall. I notced the is a hole in a (air vacuume line) would that be the issue? Or should i just change my CPS and fuel regulator. I need help guys!!
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Thread Starter
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Posts: 55
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00 S430 & 02 Suzuki 750 Katana
Haha very funny well I replaced them today, so when the weather gets hot and the temp gauge goes to around the 80 degree to 85 degree ill see if the RPM goes crazy again and if it stalls out... Ill keep u all posted
Junior Member
Joined: Nov 2008
Posts: 39
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2015 SL400 and 2004 SL500
Cats out?
Tell us about the CATS - which ones did you use? How were they installed, which O2Sensors? Big job here. I've been living with rattles from mine and with summer coming it will be noticeable with open windows. Indy thinks it might be the shields, but once he cuts those off I may have worse problems created from the heat. That worries me about any replacements I have seen.
So how is yours?
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2000 w210
CATS
NOT SURE IF YOU DID OR DID NOT REPLACE VACUUM LINE OR IF YOU WERE JOKING TO BEGIN WITH, I'M SLOW I GUESS. I SEE ALOT ON THREADS ABOUT CAT CONVERTERS AND REPLACEMRNTS. GOOGLE "MERCEDES BENZ PARTS" OR "BENCHMARK CONVERTERS" TO GET INFO. I INSTALLED ONE ON PASS SIDE OF 2000 E430, BOLT ON, NO WELDING,
Thread Starter
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Posts: 55
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00 S430 & 02 Suzuki 750 Katana
I used these CATS>>MAGNAFLOW 99000 SERIES<< They are universal.. and BOSCH O2 Sensors. I cut off the resonator and kept the mufflers. The Rattling really got to on nerves!! It sounds sooo much better coming from that V8. Well so far so good when it comes with the RPM fluctuation no more rough Idel and no stalling after I changed the Vacuume line, but it hasn't been that hott here in NJ. So once it get really hott ill take it out for a spin!!!
