GL350 lost mpg and sluggish
Thread Starter
Super Member
Joined: Aug 2008
Posts: 528
Likes: 20
From: Chicago IL
X166 gls450 2017
GL350 lost mpg and sluggish
folks any idea why the car feels sluggish and my mpg dropped to 20 highway granted my avg speed was 80.. (302 miles driven to half tank, 15.29 gallons filled) .. I'm suspecting dpf clogged or intake getting clogged due to EGR ??
Newbie
Joined: Feb 2017
Posts: 10
Likes: 2
2011 GL-350
This may not be the Issue but on all diesels this is were you ( I )start .
1: Codes ?
2: Change Fuel filter ( it may not need it but start there ( blow into the removed one
Check for restrictions ( larger orifice is inlet ) blow backwards upside down into container and see what comes out ( water particulate ? )
3: check Air cleaners ( even better new ones )
4: EGR sticking and fouled (Right side of turbo ) look online there are instructions on cleaning
5: Check fuel pressure supply side ( between fuel filter outlet "small hose " and high
Pressure Pump ( should be around 80 PSI I think ? ebay has fuel pressure kits cheap
See if that checks out if not it is good PM
HCF
1: Codes ?
2: Change Fuel filter ( it may not need it but start there ( blow into the removed one
Check for restrictions ( larger orifice is inlet ) blow backwards upside down into container and see what comes out ( water particulate ? )
3: check Air cleaners ( even better new ones )
4: EGR sticking and fouled (Right side of turbo ) look online there are instructions on cleaning
5: Check fuel pressure supply side ( between fuel filter outlet "small hose " and high
Pressure Pump ( should be around 80 PSI I think ? ebay has fuel pressure kits cheap
See if that checks out if not it is good PM
HCF
Senior Member
Joined: May 2013
Posts: 437
Likes: 84
From: Espoo, Finland
2012 GL 350
HCF, can you tell me how you remove the EGR valve on a GL? It's under the cowl up against the firewall and essentially blocked by the lift hook on the engine. Add to that it's pressed in there and basically won't budge because of soot buildup.
When I was doing my timing chain replacement, I fought with this thing for hours before I got it out by wedging under it with a screwdriver that I filed down. I'm certain this is not the way you are supposed to do it because it dings up the mating surfaces which are aluminum. I'm assuming there is a better way. All the videos that I found were on sprinters or E classes, which have much better access.
When I was doing my timing chain replacement, I fought with this thing for hours before I got it out by wedging under it with a screwdriver that I filed down. I'm certain this is not the way you are supposed to do it because it dings up the mating surfaces which are aluminum. I'm assuming there is a better way. All the videos that I found were on sprinters or E classes, which have much better access.
MBWorld Fanatic!
Joined: Dec 2004
Posts: 4,268
Likes: 253
a clogged dpf will throw errors.
at 80mph with winter blend diesel your mpg should be around 23. things like head on wind, hills will add to the mpg misery in a hurry and can drop it to 20 or thereabouts.
i would take another 30+mile trip and drive 65 or thereabouts... see if you get 25 mpg or more before you decide your truck is sick. it might simply need an alignment or your tires might be underinflated...
at 80mph with winter blend diesel your mpg should be around 23. things like head on wind, hills will add to the mpg misery in a hurry and can drop it to 20 or thereabouts.
i would take another 30+mile trip and drive 65 or thereabouts... see if you get 25 mpg or more before you decide your truck is sick. it might simply need an alignment or your tires might be underinflated...
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Newbie
Joined: Feb 2017
Posts: 10
Likes: 2
2011 GL-350
Sometimes after we do major surgery on our cars I believe we might become "Hyper Sensitive " to any little hiccup , I know I do .
I just took my 2011 GL350 on a family vacation ( 3000 miles round trip ) after some fuel delivery strife's .
I love this truck . I am however a little more skidish then when I am bombing down route 95 in my E350 7.3 powerstroke bulldozer !
How ever I digress I am well schooled with most diesel systems old and new but the
OM642 is new to me and I am learning it .
I believe you bought yours used like me so we have to guess about previous care ?
that said you also know witch end of the wrench does what .
My advise on the EGR comes from online research and not personal experience .
1. when you had your engine apart did it seem clean our fouled up .
2. ( My guess ) that the EGRs on the sprinters foul quicker because of the extra work preformed .
3 . I have noticed once and awhile my engine will be off momently then correct itself
4 . I believe once over 75 mph @ 2250 rpm our spectacular fuel economy begins to drop
Again I love this truck and it is new to me . So I will be ratcheting in on its nuance's
and reporting them to my fellow enthusiast so we can help each other out .
from what I have read I guess the EGR has to be wrestled with to be removed
is there any better access with the rear sheet metal panels under the weather strip removed ?
also maybe someone could help on calibration
HCF
I just took my 2011 GL350 on a family vacation ( 3000 miles round trip ) after some fuel delivery strife's .
I love this truck . I am however a little more skidish then when I am bombing down route 95 in my E350 7.3 powerstroke bulldozer !
How ever I digress I am well schooled with most diesel systems old and new but the
OM642 is new to me and I am learning it .
I believe you bought yours used like me so we have to guess about previous care ?
that said you also know witch end of the wrench does what .
My advise on the EGR comes from online research and not personal experience .
1. when you had your engine apart did it seem clean our fouled up .
2. ( My guess ) that the EGRs on the sprinters foul quicker because of the extra work preformed .
3 . I have noticed once and awhile my engine will be off momently then correct itself
4 . I believe once over 75 mph @ 2250 rpm our spectacular fuel economy begins to drop
Again I love this truck and it is new to me . So I will be ratcheting in on its nuance's
and reporting them to my fellow enthusiast so we can help each other out .
from what I have read I guess the EGR has to be wrestled with to be removed
is there any better access with the rear sheet metal panels under the weather strip removed ?
also maybe someone could help on calibration
HCF
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Senior Member
Joined: Mar 2009
Posts: 401
Likes: 31
From: CT
GL 450, 993TT, Cayenne Diesel, 964C4
Originally Posted by alx
a clogged dpf will throw errors.
at 80mph with winter blend diesel your mpg should be around 23. things like head on wind, hills will add to the mpg misery in a hurry and can drop it to 20 or thereabouts.
i would take another 30+mile trip and drive 65 or thereabouts... see if you get 25 mpg or more before you decide your truck is sick. it might simply need an alignment or your tires might be underinflated...
at 80mph with winter blend diesel your mpg should be around 23. things like head on wind, hills will add to the mpg misery in a hurry and can drop it to 20 or thereabouts.
i would take another 30+mile trip and drive 65 or thereabouts... see if you get 25 mpg or more before you decide your truck is sick. it might simply need an alignment or your tires might be underinflated...
Senior Member
Joined: May 2013
Posts: 437
Likes: 84
From: Espoo, Finland
2012 GL 350
"from what I have read I guess the EGR has to be wrestled with to be removed
is there any better access with the rear sheet metal panels under the weather strip removed ? "
Wrestled with is one way to put it. I struggled with it for hours, mangled the case, broke the little plastic cover and finally resorted to wedging it from the bottom which gouged the mounting surface.
When I got it off, it wasn't that dirty, though I did clean it thoroughly before I reinstalled it. I only needed to remove it in order to remove the left valve cover; it obstructs the bolt in the rear corner. I did remove the sheet metal panels but that is no help. I'm a damn good mechanic and it's amazing how much time I wasted trying to remove it. I tried nearly everything in the book and none of it worked. The factory procedure is no help "lift out from above" I believe it says. Thanks...but it's too much money for a replacement so I was being careful not to destroy it.
is there any better access with the rear sheet metal panels under the weather strip removed ? "
Wrestled with is one way to put it. I struggled with it for hours, mangled the case, broke the little plastic cover and finally resorted to wedging it from the bottom which gouged the mounting surface.
When I got it off, it wasn't that dirty, though I did clean it thoroughly before I reinstalled it. I only needed to remove it in order to remove the left valve cover; it obstructs the bolt in the rear corner. I did remove the sheet metal panels but that is no help. I'm a damn good mechanic and it's amazing how much time I wasted trying to remove it. I tried nearly everything in the book and none of it worked. The factory procedure is no help "lift out from above" I believe it says. Thanks...but it's too much money for a replacement so I was being careful not to destroy it.
