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4x4abc
Date registered: Apr 2006
Location: La Paz, Baja California, Mexico
Vehicle(s): 02 G500
| G500 rough idle
my wonderful G500 does not idle as smoothly as it used to idle
runs fine at all speeds
fuel consumption unchanged
a little rough at 650
really rough at 1,200
OK after that
ran a systems check with Karl a few days ago
no codes - no errors
what should I do? |
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Gilamonster
Veteran
Date registered: Sep 2013
Location: New Mexico
Vehicle(s): G #1 (mix of a 460, 461 & 463), #2 is a 2000 G500
Posts: 151
| RE: G500 rough idle
Harald,
I'm a relative novice when it comes to G's so I write this with a bit of apprehension.
For a rough idle I'd first consider my fuel source. Try a different fuel station and see if idle improves.
Second I'd look at my air filter. I'm sure you've already checked this.
Third is spark. Even one compromised plug/cable will compromise the smoothness of a V8. With 16 of each on a G500 the odds of a spark issue are increased twofold.
William
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gerryvz
Extreme Veteran
Date registered: Apr 2014
Location: Annapolis, MD
Vehicle(s): 1994 G320, 1989 560SEC, 1994 E500 (W124)
Posts: 336
| Re: G500 rough idle
You should get a smoke test to see if there are any vacuum leaks in the intake air system. |
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4x4abc
Date registered: Apr 2006
Location: La Paz, Baja California, Mexico
Vehicle(s): 02 G500
| RE: G500 rough idle
I did not check the air filter lately
will do
come to think of it, the spark plugs are about 120k miles old
will get new ones
any advice on how to change them best? |
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J.R.
Elite Veteran
Date registered: Apr 2006
Location: Southern Maryland
Vehicle(s): 00 G500, 09 911 4S, 11 Cayenne S, 86 280GE (sold)
Posts: 828
| RE: G500 rough idle
Harald,
Another excellent DIY by G-AMG that will serve you well. http://www.pointedthree.com/disc/forums/showthread.php?tid=17088&po...
I always remove the coil packs because it gives me a chance to inspect their casings and electrical connections, etc.
Stick with the plugs called for by Mercedes, not necessarily what shows up in the aftermarket parts supplier's catalogs. They do like to sell pricey plugs that do not necessarily work the best. In Apr of 2014, I ordered 16 plugs part number 003-159-94-03 and inside the mercedes box were NGK PFR5R11, and there are several other brands that show up.
Edited by J.R. 2/21/2015 10:44 AM
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Titus Pullo
Elite Veteran
Date registered: May 2007
Location: Ottawa, ON, Canada
Vehicle(s): '90 Wolf 240GD, '06 G270 CDI.
Posts: 1010
| RE: G500 rough idle
spark plugs, air, fuel filters, injector clean, throttle body clean. |
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Roly
Elite Veteran
Date registered: Apr 2006
Location: Australia
Vehicle(s): 1999 G500
Posts: 661
| RE: G500 rough idle
If you are connected to a DAS pc, there is an option to test the 'rough running'. The screen displays a table with the performance of each cylinder and can be compared to the standard. If one cylinder is out of spec, then you can investigate. |
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4x4abc
Date registered: Apr 2006
Location: La Paz, Baja California, Mexico
Vehicle(s): 02 G500
| RE: G500 rough idle
we ran DAS with 'rough running' selected - no table of individual cylinders though |
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Roly
Elite Veteran
Date registered: Apr 2006
Location: Australia
Vehicle(s): 1999 G500
Posts: 661
| RE: G500 rough idle
You should be able dis display a screen like the one in the pdf
Attachments
----------------
 misfire screen.pdf (15KB - 36 downloads)
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Otiswesty
Administrator
Date registered: Jun 2007
Location: Portland, Oregon
Vehicle(s): 463.241, 461.213
Posts: 3004
| Re: G500 rough idle
If you do your plugs, make sure to check the gap and not assume they are spec out of the box. |
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4x4abc
Date registered: Apr 2006
Location: La Paz, Baja California, Mexico
Vehicle(s): 02 G500
| Re: G500 rough idle
now here is a thought - I noticed that my fan is not spinning freely any longer with engine off
viscous dead
could that be a cause for the vibrations I feel especially at first startup in the morning? |
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WEBIII
Extreme Veteran
Date registered: Oct 2010
Location: Inlet Beach, FL
Vehicle(s): 461.318, 463.241
Posts: 315
| Re: G500 rough idle
Harald -- curious of you got this rough idle smoothed out?
Winston |
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4x4abc
Date registered: Apr 2006
Location: La Paz, Baja California, Mexico
Vehicle(s): 02 G500
| Re: G500 rough idle
WEBIII - 5/27/2015 9:28 AM
Harald -- curious of you got this rough idle smoothed out?
Winston
in fact, I did
it was exactly as I thought, viscous coupling and water pump
and the frozen fan clutch may have killed the water pump bearing
replaced both and the truck runs like new
http://www.pointedthree.com/disc/forums/showthread.php?tid=22292&po... |
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WEBIII
Extreme Veteran
Date registered: Oct 2010
Location: Inlet Beach, FL
Vehicle(s): 461.318, 463.241
Posts: 315
| Re: G500 rough idle
Good to hear it's back to normal. my G500 has the slightest shake at idle and the fan turns with what feels like the right amount of resistance when cold. I think I'll start with plugs -- no record of them ever being changed and now the truck has 72k miles. |
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