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· Registered
1987 560SL
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141 Posts
Discussion Starter · #1 ·
2004 C240 2.6L

Pulled codes a few days ago and showed both bank 1 and bank 2 lean. Connected scanner and based on diagnostics, seemed MAF was at fault. MAF was replaced two months ago. Exchanged MAF for new replacement under warranty. Drove car for awhile and threw another code. This time code is P0174 Lean Bank 2. P0171 no longer appears. Checked for intake leaks with water and found none. Plugs, wires and ignition coils are new. Most vacuum lines have been replaced. Intake manifold has been replaced.

When I now drive the car, with AC on there is very noticeable lag. As speed and rpm increase car drives much better. mileage with this one code is 17 mpg on average. usually is low 20's. O2 sensors were replaced a couple of weeks ago.

At this point, just not sure what the problem could be.

Bob
 

· Coupe/Convertible Forums Moderator
CURRENT: 2011 SL550 FORMER: C300, ML350, CLK550 Cabriolet, C240, ML320, 300TD
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25,452 Posts
Where are you getting these MAF sensors? If it's Amazon or eBay, they are probably fake Chinese "Bosch" parts.
 

· Coupe/Convertible Forums Moderator
CURRENT: 2011 SL550 FORMER: C300, ML350, CLK550 Cabriolet, C240, ML320, 300TD
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25,452 Posts
That codes is either a bad MAF sensor, or possibly a problem with the coolant temperature sensor. Proper diagnosis requires SDS to test the actual values, otherwise it's just throwing parts at it.

Another thing to try - unplug the MAF sensor and see if performance/economy improves or not. If there is no change, then it's probably not the MAF. IF it improves, then it may be a bad MAF.
 

· Registered
1987 560SL
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141 Posts
Discussion Starter · #5 ·
Napa Auto Parts

Where are you getting these MAF sensors? If it's Amazon or eBay, they are probably fake Chinese "Bosch" parts.
Was also receiving code P20d4. Finally my wife took the car into the Mercedes dealer to run diagnostics. Diagnostics reported that MAF was bad. I explained to them previous shop replaced the MAF twice which was sourced from Napa Auto Parts. Dealer said they have run into this problem before with inferior parts. The first MAF from napa was bosch and the second replacement was TDI or TMI I don't recall which. Dealer put in Mercedes part and car ran perfectly! I will try to get a refund on the MAF that is defective. I always thought parts from NAPA were good quality - to get two inferior MAFS sequentially from them does not speak well of them.

So for the dealer to address the problem my cost breakdown was:

Diagnostic Fee 159.00
Labor to install MAF 84.00
Mercedes MAF part 298.00

Oh well, live and learn I guess......the dealer gave me a break on the MAF price, at first they wanted 450.00 for the MAF......

Car runs perfectly now with cold AC and cooling fan operating properly....finally replaced it.
 

· Registered
99 c230k
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143 Posts
People!! Stop buying shit Napa/AutoZone parts! Especially engine/electrical components...unless you have the capability of diagnosing if the "new" part is faulty you're just going to be chasing your tail.

Sent from my XT1635-01 using Tapatalk
 

· Coupe/Convertible Forums Moderator
CURRENT: 2011 SL550 FORMER: C300, ML350, CLK550 Cabriolet, C240, ML320, 300TD
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25,452 Posts
I have and Advance Auto start and alternator in the SL and they work just fine. Both have lifetime warranties so other than spending my time to R&R, I'll not worry about them again.

I think the issue is that there are "fake parts" out there. Chinese factories are making fake Bosch parts that end up being sold as genuine from what we expect to be reputable suppliers. It's a huge problem that we will continue to deal with until we crack down on imports.
 

· W220 Moderator
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9,046 Posts
Hi,

Glad you got it sorted, yeah there's a lot of Chinese Sh!te about these days.

Just for info, in case someone doesn't know this..............

When you get a "Too Lean" Code, it means that the ME has trimmed it's fuelling to the limit of its "Lean" parameters, which in lay-mans terms tells you that the Engine is running too RICH, hence the need for the ME to go to full lean settings............

The Vice Versa applies, i.e. "Too Rich" Code = Engine is actually running Lean :wink

Can be confusing unless you understand how the Fuel Trim Strategies work and are programmed :wink

HTH,

Cheers Dave
 

· Registered
1987 560SL
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141 Posts
Discussion Starter · #9 ·
Yes this was a problem from hell. The car drives perfectly now. Had to put a couple of thousand in parts to bring the car to factory condition. I really enjoy no car payments! Keeps the insurance premium low as well......

My brother is assisting me in installing the footwell actuator kit. Once this is installed, no problems remain.....finally!
 
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