Running lean on highway
Thread Starter
Senior Member
Joined: Feb 2012
Posts: 299
Likes: 1
From: London
2004 E55K AMG Wagon
Running lean on highway
3 times today had the following
Driving with traffic flowing 65-80 mph light throttle then a hesitation, noticed AFR signals lean and no matter what throttle position was showing 16-18 !
Pulled over and car was erratic idle, checked for codes and nothing. Switched off restart and all is OK but will then repeat 20 miles or so later.
3rd time checked fuel trims before shutting down and short trim banks 1 and 2 show +15% but 02 sensors and wideband show lean. Still no codes.
A few days ago I had the throttle body and fuel rail/injectors off but surely a fitting issue would show up at other times not just highway driving?
Driving with traffic flowing 65-80 mph light throttle then a hesitation, noticed AFR signals lean and no matter what throttle position was showing 16-18 !
Pulled over and car was erratic idle, checked for codes and nothing. Switched off restart and all is OK but will then repeat 20 miles or so later.
3rd time checked fuel trims before shutting down and short trim banks 1 and 2 show +15% but 02 sensors and wideband show lean. Still no codes.
A few days ago I had the throttle body and fuel rail/injectors off but surely a fitting issue would show up at other times not just highway driving?
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Joined: Jun 2010
Posts: 4,173
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From: Puerto Rico
2005 E55 AMG
3 times today had the following
Driving with traffic flowing 65-80 mph light throttle then a hesitation, noticed AFR signals lean and no matter what throttle position was showing 16-18 !
Pulled over and car was erratic idle, checked for codes and nothing. Switched off restart and all is OK but will then repeat 20 miles or so later.
3rd time checked fuel trims before shutting down and short trim banks 1 and 2 show +15% but 02 sensors and wideband show lean. Still no codes.
A few days ago I had the throttle body and fuel rail/injectors off but surely a fitting issue would show up at other times not just highway driving?
Driving with traffic flowing 65-80 mph light throttle then a hesitation, noticed AFR signals lean and no matter what throttle position was showing 16-18 !
Pulled over and car was erratic idle, checked for codes and nothing. Switched off restart and all is OK but will then repeat 20 miles or so later.
3rd time checked fuel trims before shutting down and short trim banks 1 and 2 show +15% but 02 sensors and wideband show lean. Still no codes.
A few days ago I had the throttle body and fuel rail/injectors off but surely a fitting issue would show up at other times not just highway driving?
MBWorld Fanatic!
Joined: Jun 2010
Posts: 4,173
Likes: 7
From: Puerto Rico
2005 E55 AMG
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Joined: May 2011
Posts: 1,109
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From: Las Vegas, NV
1000Hp Diesel Trucks, 2019 E63s
Well, I've had it happened and verified it with STAR. I can assure you it isn't able to compensate for it under light throttle or at idle. When I've had it happen the symptoms are identical to what the OP described.
MBWorld Fanatic!
Joined: Jun 2010
Posts: 4,173
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From: Puerto Rico
2005 E55 AMG
MBWorld Fanatic!
Joined: May 2011
Posts: 1,109
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From: Las Vegas, NV
1000Hp Diesel Trucks, 2019 E63s
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Thread Starter
Senior Member
Joined: Feb 2012
Posts: 299
Likes: 1
From: London
2004 E55K AMG Wagon
Well get that checked but at 80mph surely the supercharger must be engaged anyway as the RPM would be >2200.
The weird thing is the way the AFR flips so violently from hovering around 14.5-15.2 then the stutter and AFR registers off the scale. With increased throttle it flickers around 16-17 but will not return. Injector Duty Cycle remains the same at 10% but as said earlier short fuel is then +15% but both the 02 primary sensors and my wideband show the exhaust is lean.
The weird thing is the way the AFR flips so violently from hovering around 14.5-15.2 then the stutter and AFR registers off the scale. With increased throttle it flickers around 16-17 but will not return. Injector Duty Cycle remains the same at 10% but as said earlier short fuel is then +15% but both the 02 primary sensors and my wideband show the exhaust is lean.
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MBWorld Fanatic!
Joined: May 2011
Posts: 1,109
Likes: 20
From: Las Vegas, NV
1000Hp Diesel Trucks, 2019 E63s
Well get that checked but at 80mph surely the supercharger must be engaged anyway as the RPM would be >2200.
The weird thing is the way the AFR flips so violently from hovering around 14.5-15.2 then the stutter and AFR registers off the scale. With increased throttle it flickers around 16-17 but will not return. Injector Duty Cycle remains the same at 10% but as said earlier short fuel is then +15% but both the 02 primary sensors and my wideband show the exhaust is lean.
The weird thing is the way the AFR flips so violently from hovering around 14.5-15.2 then the stutter and AFR registers off the scale. With increased throttle it flickers around 16-17 but will not return. Injector Duty Cycle remains the same at 10% but as said earlier short fuel is then +15% but both the 02 primary sensors and my wideband show the exhaust is lean.
Last edited by PACougar; Oct 29, 2012 at 04:07 AM.
Thread Starter
Senior Member
Joined: Feb 2012
Posts: 299
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From: London
2004 E55K AMG Wagon
PACougar 
Thanks, it was the clutch sticking on. I just had the S/C Pulley Clutch fitted a couple of weeks ago and it was checked in the workshop and run up to working temp. However when the car is driven for longer periods the additional heat causes expansion and the pulley catches and stays on. Looks like I need to put another shim in there.
Thanks, it was the clutch sticking on. I just had the S/C Pulley Clutch fitted a couple of weeks ago and it was checked in the workshop and run up to working temp. However when the car is driven for longer periods the additional heat causes expansion and the pulley catches and stays on. Looks like I need to put another shim in there.
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Joined: May 2011
Posts: 1,109
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From: Las Vegas, NV
1000Hp Diesel Trucks, 2019 E63s
PACougar
Thanks, it was the clutch sticking on. I just had the S/C Pulley Clutch fitted a couple of weeks ago and it was checked in the workshop and run up to working temp. However when the car is driven for longer periods the additional heat causes expansion and the pulley catches and stays on. Looks like I need to put another shim in there.
Thanks, it was the clutch sticking on. I just had the S/C Pulley Clutch fitted a couple of weeks ago and it was checked in the workshop and run up to working temp. However when the car is driven for longer periods the additional heat causes expansion and the pulley catches and stays on. Looks like I need to put another shim in there.
Thread Starter
Senior Member
Joined: Feb 2012
Posts: 299
Likes: 1
From: London
2004 E55K AMG Wagon
MBWorld Fanatic!
Joined: May 2011
Posts: 1,109
Likes: 20
From: Las Vegas, NV
1000Hp Diesel Trucks, 2019 E63s
