Right bank lean
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Junior Member
Joined: Mar 2014
Posts: 23
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From: Minneapolis
07 CLK63
Right bank lean
I've been getting check engine code popping up every month or two saying right bank lean on my CLK63 cab. Dealer has performed a test or two ruling out MAFS and a few other things with no luck finding a problem. I replaced the oil dipstick with an MB upgraded two rubber gaskets one with no help in problem. Dealer mentioned a particular gasket or maybe valves on right bank was somewhat common problem with these motors. Has anyone else had this problem? If so, I wonder if my 3rd party powertrain warranty would maybe cover this if this is the problem.
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From: Austin, TX
2006 E55, 2012 GLK350 & 1992 190e sportline
I wonder if my 3rd party powertrain warranty would maybe cover this if this is the problem.
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Joined: Oct 2012
Posts: 1,427
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From: Florida
2002 CLK 55 AMG cabriolet Eurocharged
If you could get the O2 sensor readings off of a scanner it might help us.
I get right bank lean from a restricted cat, The exhaust gases build up in between the cats and random throw the same code.
Other lean conditions can be from low fuel delivery hence clogged filters.
A 4 gas reading from the tail pipe will tell us about other issues like degraded plugs, wires, intake manifold leak and oil consumption. Compression or oil ring culprit.
A burnt valve or seat in the cylinder head will throw the code but the engine will run poorly.
An infrared temp gun or pyrometer can be used for testing the cats without much work. Test temp in and out each bank each cat and observe difference.
Based on the age it is likely a lazy sensor which does not work properly all the time, mileage unknown.
Gator
I get right bank lean from a restricted cat, The exhaust gases build up in between the cats and random throw the same code.
Other lean conditions can be from low fuel delivery hence clogged filters.
A 4 gas reading from the tail pipe will tell us about other issues like degraded plugs, wires, intake manifold leak and oil consumption. Compression or oil ring culprit.
A burnt valve or seat in the cylinder head will throw the code but the engine will run poorly.
An infrared temp gun or pyrometer can be used for testing the cats without much work. Test temp in and out each bank each cat and observe difference.
Based on the age it is likely a lazy sensor which does not work properly all the time, mileage unknown.
Gator
Thread Starter
Junior Member
Joined: Mar 2014
Posts: 23
Likes: 0
From: Minneapolis
07 CLK63
If you could get the O2 sensor readings off of a scanner it might help us.
I get right bank lean from a restricted cat, The exhaust gases build up in between the cats and random throw the same code.
Other lean conditions can be from low fuel delivery hence clogged filters.
A 4 gas reading from the tail pipe will tell us about other issues like degraded plugs, wires, intake manifold leak and oil consumption. Compression or oil ring culprit.
A burnt valve or seat in the cylinder head will throw the code but the engine will run poorly.
An infrared temp gun or pyrometer can be used for testing the cats without much work. Test temp in and out each bank each cat and observe difference.
Based on the age it is likely a lazy sensor which does not work properly all the time, mileage unknown.
Gator
I get right bank lean from a restricted cat, The exhaust gases build up in between the cats and random throw the same code.
Other lean conditions can be from low fuel delivery hence clogged filters.
A 4 gas reading from the tail pipe will tell us about other issues like degraded plugs, wires, intake manifold leak and oil consumption. Compression or oil ring culprit.
A burnt valve or seat in the cylinder head will throw the code but the engine will run poorly.
An infrared temp gun or pyrometer can be used for testing the cats without much work. Test temp in and out each bank each cat and observe difference.
Based on the age it is likely a lazy sensor which does not work properly all the time, mileage unknown.
Gator
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Joined: Oct 2012
Posts: 1,427
Likes: 100
From: Florida
2002 CLK 55 AMG cabriolet Eurocharged
The oxygen enriched fuel reminds me of AV gas or Aviation fuel. Aviation fuel is enriched with octane boost and oxygen for NA (naturally aspirated) engines to survive in high altitude where oxygen is depleted.
We used to mix it with pump gas when racing fuel for cars ran short. It contained lead when I used it not sure now.
Both lead and avgas will deter the reading for the o2 sensors. The oxygen enriched fuel is a dead give away for lean condition. It might save some mpg but the computer does not know how to compute the change.
Full aviation fuel engines must be properly tuned for the addded octane and oxygen for benefit.
Most of todays pump fuel contains up to 10% ethyl alcohol. Alcohol burns twice the rate of pump petroleum and increases combustion temperatures for some.
We used alcohol since the 50's for race engines but h2o was misted to cool the combustion temps and utilize the octane rating plus combustion rate of 2:1.
Go back to premium pump gas and report. The o2 sensor will react to an abnormal burn and is likely what is happening here.
Best, Gator
We used to mix it with pump gas when racing fuel for cars ran short. It contained lead when I used it not sure now.
Both lead and avgas will deter the reading for the o2 sensors. The oxygen enriched fuel is a dead give away for lean condition. It might save some mpg but the computer does not know how to compute the change.
Full aviation fuel engines must be properly tuned for the addded octane and oxygen for benefit.
Most of todays pump fuel contains up to 10% ethyl alcohol. Alcohol burns twice the rate of pump petroleum and increases combustion temperatures for some.
We used alcohol since the 50's for race engines but h2o was misted to cool the combustion temps and utilize the octane rating plus combustion rate of 2:1.
Go back to premium pump gas and report. The o2 sensor will react to an abnormal burn and is likely what is happening here.
Best, Gator
Last edited by GatorMB; Oct 22, 2015 at 10:40 AM. Reason: spelling
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Joined: Apr 2005
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Likes: 84
From: SCV SoCal
2002 CLK430
I agree with Gator. Here’s why
The ONLY way an ECU knows whether the engine is running lean is by examining the exhaust. The O2 sensor is what the ECU uses to inspect the exhaust’s oxygen content. If the O2 sensor detects 3% or less oxygen in the exhaust, it signals the ECU that the engine is running lean by sending low voltage - something below 0.3 volts. If the exhaust has 0% oxygen, the engine is running rich. In that case, the O2 sensor will produce something above 0.6 volts. O2 sensors regularly swap back and forth between the 0.45 volt rich/lean points.
Oxygen sensors are normal wear parts. Know what they do when they do when they’re worn out? They produce low voltage. The ECU sees that low voltage and increases the fuel flow on the lean running bank. Eventually, the ECU determines that it’s adjusted the flow rate enough and something else must be wrong. That’s when it illuminates the check engine light. Why does it stop adjusting the rate? Because that overly rich bank that’s still reading lean is obviously not lean. BTW, an overly rich exhaust will kill a catalytic converter. Although Bosch says their O2 sensors “can” last over 100,000 miles, that’s either under lab conditions or in SoCal where many people put 100K on a car in 3 years. You’ve got a 9 year old car with 70K on it. The primary sensor is probably on its way out. I’d replace both of them. In fact, I did on mine. At the 9 year point. You can spend a lot of money on diagnostics, but you may find the investigative analytics to cost more than the replacement parts.
I hope that helps.
The ONLY way an ECU knows whether the engine is running lean is by examining the exhaust. The O2 sensor is what the ECU uses to inspect the exhaust’s oxygen content. If the O2 sensor detects 3% or less oxygen in the exhaust, it signals the ECU that the engine is running lean by sending low voltage - something below 0.3 volts. If the exhaust has 0% oxygen, the engine is running rich. In that case, the O2 sensor will produce something above 0.6 volts. O2 sensors regularly swap back and forth between the 0.45 volt rich/lean points.
Oxygen sensors are normal wear parts. Know what they do when they do when they’re worn out? They produce low voltage. The ECU sees that low voltage and increases the fuel flow on the lean running bank. Eventually, the ECU determines that it’s adjusted the flow rate enough and something else must be wrong. That’s when it illuminates the check engine light. Why does it stop adjusting the rate? Because that overly rich bank that’s still reading lean is obviously not lean. BTW, an overly rich exhaust will kill a catalytic converter. Although Bosch says their O2 sensors “can” last over 100,000 miles, that’s either under lab conditions or in SoCal where many people put 100K on a car in 3 years. You’ve got a 9 year old car with 70K on it. The primary sensor is probably on its way out. I’d replace both of them. In fact, I did on mine. At the 9 year point. You can spend a lot of money on diagnostics, but you may find the investigative analytics to cost more than the replacement parts.
I hope that helps.
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Thread Starter
Junior Member
Joined: Mar 2014
Posts: 23
Likes: 0
From: Minneapolis
07 CLK63
I took it to the dealer and ran a smoke test and figured it out. The right intake manifold gasket was leaking causing the problem. Had them replace both, problem fixed. Thank you everyone for helping me out on this! 
