Low Power - No Code
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2008 Mercedes Benz ML 320 CDI
Low Power - No Code
I am driving a 2008 ML 320CDI. Today I had an episode of what I thought might be the "limp home" mode for a few miles. No "check engine" light appeared. The transmission would not kick down and engine RPMs stayed under 2500. This lasted for about five miles. I used the paddle shifters to shift to a lower gear but performance remained sluggish. I pulled over and restarted the engine, but the condition continued. I pulled over again after a few miles and shifted to neutral. The engine was running smoothly but would not rev over 3000 RPM in neutral. After idling for a while I pulled out in traffic again and found the condition had disappeared. "Limp Home" supposedly uses only second gear and speeds are limited to under 30 MPH. I reached 6th gear and 50, but had low power. It is possible that fuel pressure was low; I had changed my fuel filter last month and in removing the FI inlet hose, provoked a pinhole leak. I replaced it with new hose from a bulk supply that had not been pre-formed. The new hose would not bend without kinking. But the fuel supply was adequate enough for the engine to run without adverse symptoms for two weeks. I have had low fuel pressure (driving uphill with nearly empty tank) once before and encountered "limp home" mode, but it was accompanied by a "check engine" code for "low fuel rail pressure". I have ordered a pre-formed hose from MB to replace my kinked hose in case this was the source of trouble. But I am puzzled about the problem occurring without a sensor detecting it. Any ideas?
Last edited by dpulling; Aug 28, 2015 at 01:02 AM.
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Joined: Feb 2015
Posts: 116
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From: Ontario, Canada
2013 GLK250 Bluetec
Was it accompanied by any odd noises, smoke or other visual ques etc? Did you do a fluid check, oil dipstick looking ok no sludge or water or anything weird looking?
The fuel filter was it oem or other brand, perhaps its gone bad or failed in some away since it was just replaced...
Just some thoughts and quick checks.. Hope it helps
The fuel filter was it oem or other brand, perhaps its gone bad or failed in some away since it was just replaced...
Just some thoughts and quick checks.. Hope it helps
Thread Starter
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2008 Mercedes Benz ML 320 CDI
Nothing odd except the lack of power. The condition is gone. I towed a 6000 pound trailer today without problems. If there were any component failures (filters) it would not have recovered and run fine. I called the shop where I have work done and they said without "check engine" alerts, no codes would appear. They said don't bother bringing it in if it is running OK. I suspect that hose and will replace it.
Thanks for your replies.
Thanks for your replies.
MBWorld Fanatic!
Joined: Jun 2006
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From: Nova Scotia, Canada
2023 GLK250, 1987 560SL
That's not exactly correct. If you have a proper reader that can read all the proprietary codes, it will store some in there despite no check engine light.
Thread Starter
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2008 Mercedes Benz ML 320 CDI
Sorry for the late response and thanks for yours. I replaced the hose with a kinkless one from MB and took a trip this month pulling a 6000 lb. camper through Oregon. In 2000 miles, many through mountains, the power loss episode occurred once, at startup (hasn't happened underway), and was restored by a restart. It was definitely not "limp home" since I could shift through gears with the paddle. I suspect something with "drive by wire" throttle connections. I will read codes at your suggestion to see if any were left.
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MBWorld Fanatic!
Joined: Jun 2006
Posts: 1,140
Likes: 118
From: Nova Scotia, Canada
2023 GLK250, 1987 560SL
That could be the problem also. There is a module for this, sometimes it's mounted behind the accelerator like in the w203 C-classes, and sometimes in the engine bay like in the w208 CLK's. It could have some grime in it, if it's behind the accelerator.
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