P0172 OBDII, MAF, Spark Plugs, PCV hose fix and my 2 cents
Thread Starter
Senior Member
Joined: Apr 2002
Posts: 405
Likes: 12
From: Sacramento, CA
W204 C300 2010
P0172 OBDII, MAF, Spark Plugs, PCV hose fix and my 2 cents
My wife's C230K had been experiencing decline in idle quality over a period of about 3 months. The car has logged about about 50K miles. Initially, it was a slight lumpy idle, then a periodic CEL or "check engine light", the first CEL's P0 numbers indicated "... misfire bank ???" I can't remember the code. And then towards the last month, the famed P0172 code - over rich mixture.
Researching the web is good and bad when trying to diagnose car problems. One symptom can be related to many parts and each person's interpretation can be slightly different. When the idle first a little lumpy, I was able to spray copious amounts of CRC MAF cleaner on the MAF. First, just thru the metal mesh with the air cleaner removed and then the big plunge of removing he airbox with MAF. When the idle seem to improve slightly and then go back, I was sure that I needed a new MAF, from which I did order from the Arizona parts house. I go the Siemens unit for $276.
Next, this was not the main problem, I no longer saw the misfire code, but now the P0172 OBDII CEL code. I remembered this link:
https://mbworld.org/forums/showthrea...&highlight=pcv
I had not really paid much attention to the overall content, only that the description on how to remove the air box was very good. When I plugged in P0172 in this mbworld.org forum search engine, I was indirectly pointed back to this page. I then read each line, by line, and over again. I had missed the cracked PCV hose issue altogether!
This may be in another post, but the PCV hose part number has been updated from A203-018-12-82 to 271-018-12-82. My price August 29, 2008 was $14.24 plus CA sales tax from Mercedes Benz of Sacramento.
After many cleanings of the MAF, I have gotten very proficient in removing the air box. Takes only about 5 minutes now. The lower intake connection now has a hose clamp with a thumbscrew, I can untwist this connection with my fingers. The hardest part is reassembly when getting the air box tube back into the rubber hose. I use a little spray lube to allow the parts to slide together easier. Do not use silicone spray, it is supposed to be bad for the O2 sensors.
Along the way, I also had put in many bottles of Chevron Techron in the gas, changed the spark plugs with the magic hope of not seeing the CEL and fixing the now very lumpy idle.
The hose was purchased and I replaced it. The old one had a crack in the middle of the hose, not near the ends where the hose clamps are placed. There is not an easy way to describe the replacement, the hose slips on to the attachment nipples very easily. But the securing or tightening of the lower hose clamp is extremely tedious and is a real b!tch! Sorry, the stock clamp is a spring clamp that the MBZ techs must have a special set of pliers to remove and replace. For the home want a be fixer, I chose the basic screw on clamp (as suggested by the other post). If you can substitute the screw on with a spring clamp and have the a special tool, this is the way to do it.
Here are some pictures of the hose. Even after removing and replacing the air box, I was not looking for the cracked hose, but it is very obvious. I tore off the flap on the hose so you can see the large split. The lower hose clamp is the bear of the task.
2 cents - All of the info found on the web was good, but you have to be open minded to really figure out what the problem could be. At home, I don't have the proper equipment to truly test all parts. All in all, with the replacement the hose, plugs, MAF and the use of Techron. The car seems to run very smooth now. Power in the mid-band seems to come back alive.
Thanks,
-rob
Researching the web is good and bad when trying to diagnose car problems. One symptom can be related to many parts and each person's interpretation can be slightly different. When the idle first a little lumpy, I was able to spray copious amounts of CRC MAF cleaner on the MAF. First, just thru the metal mesh with the air cleaner removed and then the big plunge of removing he airbox with MAF. When the idle seem to improve slightly and then go back, I was sure that I needed a new MAF, from which I did order from the Arizona parts house. I go the Siemens unit for $276.
Next, this was not the main problem, I no longer saw the misfire code, but now the P0172 OBDII CEL code. I remembered this link:
https://mbworld.org/forums/showthrea...&highlight=pcv
I had not really paid much attention to the overall content, only that the description on how to remove the air box was very good. When I plugged in P0172 in this mbworld.org forum search engine, I was indirectly pointed back to this page. I then read each line, by line, and over again. I had missed the cracked PCV hose issue altogether!
This may be in another post, but the PCV hose part number has been updated from A203-018-12-82 to 271-018-12-82. My price August 29, 2008 was $14.24 plus CA sales tax from Mercedes Benz of Sacramento.
After many cleanings of the MAF, I have gotten very proficient in removing the air box. Takes only about 5 minutes now. The lower intake connection now has a hose clamp with a thumbscrew, I can untwist this connection with my fingers. The hardest part is reassembly when getting the air box tube back into the rubber hose. I use a little spray lube to allow the parts to slide together easier. Do not use silicone spray, it is supposed to be bad for the O2 sensors.
Along the way, I also had put in many bottles of Chevron Techron in the gas, changed the spark plugs with the magic hope of not seeing the CEL and fixing the now very lumpy idle.
The hose was purchased and I replaced it. The old one had a crack in the middle of the hose, not near the ends where the hose clamps are placed. There is not an easy way to describe the replacement, the hose slips on to the attachment nipples very easily. But the securing or tightening of the lower hose clamp is extremely tedious and is a real b!tch! Sorry, the stock clamp is a spring clamp that the MBZ techs must have a special set of pliers to remove and replace. For the home want a be fixer, I chose the basic screw on clamp (as suggested by the other post). If you can substitute the screw on with a spring clamp and have the a special tool, this is the way to do it.
Here are some pictures of the hose. Even after removing and replacing the air box, I was not looking for the cracked hose, but it is very obvious. I tore off the flap on the hose so you can see the large split. The lower hose clamp is the bear of the task.
2 cents - All of the info found on the web was good, but you have to be open minded to really figure out what the problem could be. At home, I don't have the proper equipment to truly test all parts. All in all, with the replacement the hose, plugs, MAF and the use of Techron. The car seems to run very smooth now. Power in the mid-band seems to come back alive.
Thanks,
-rob
Last edited by rob_fed; Sep 1, 2008 at 02:37 PM.
Super Moderator
Joined: Jul 2006
Posts: 3,365
Likes: 12
From: Orange County, CA
GMC - Miata - Trek - P-Car
Take it easy Charlie.
He has earned the satisfaction from having done it himself.
For less hearty souls, there’s this thread.
He has earned the satisfaction from having done it himself.
For less hearty souls, there’s this thread.
Thread Starter
Senior Member
Joined: Apr 2002
Posts: 405
Likes: 12
From: Sacramento, CA
W204 C300 2010
Thanks Splinter 
Timing, so far, my wife's car has had few problems and by her request has remained unmodified since new. So much so I haven't followed this forum with as much diligence as when I had my '99 W210. I saw the "free work" thread about the same time as the "hose" thread. I noticed that no one had updated the "free work" thread since March and I just wanted to try one more thing before taking it to the dealer or local independent shop as I no longer have a warranty. Hindsight would indicate the problem would of been fixed if I had to take it in to the dealer. I am just glad I was able to fix it without an extra trip. Thanks again to everyone that participates on mbworld.org, this has always been a great place containing a wealth of information. Everyone here seems to be good people.
Timing, so far, my wife's car has had few problems and by her request has remained unmodified since new. So much so I haven't followed this forum with as much diligence as when I had my '99 W210. I saw the "free work" thread about the same time as the "hose" thread. I noticed that no one had updated the "free work" thread since March and I just wanted to try one more thing before taking it to the dealer or local independent shop as I no longer have a warranty. Hindsight would indicate the problem would of been fixed if I had to take it in to the dealer. I am just glad I was able to fix it without an extra trip. Thanks again to everyone that participates on mbworld.org, this has always been a great place containing a wealth of information. Everyone here seems to be good people.
Newbie
Joined: Jun 2014
Posts: 1
Likes: 1
C230 coupe Kompressor
Still in the Sacramento area?
I have the same problem now.
My wife's C230K had been experiencing decline in idle quality over a period of about 3 months. The car has logged about about 50K miles. Initially, it was a slight lumpy idle, then a periodic CEL or "check engine light", the first CEL's P0 numbers indicated "... misfire bank ???" I can't remember the code. And then towards the last month, the famed P0172 code - over rich mixture.
Researching the web is good and bad when trying to diagnose car problems. One symptom can be related to many parts and each person's interpretation can be slightly different. When the idle first a little lumpy, I was able to spray copious amounts of CRC MAF cleaner on the MAF. First, just thru the metal mesh with the air cleaner removed and then the big plunge of removing he airbox with MAF. When the idle seem to improve slightly and then go back, I was sure that I needed a new MAF, from which I did order from the Arizona parts house. I go the Siemens unit for $276.
Next, this was not the main problem, I no longer saw the misfire code, but now the P0172 OBDII CEL code. I remembered this link:
https://mbworld.org/forums/showthrea...&highlight=pcv
I had not really paid much attention to the overall content, only that the description on how to remove the air box was very good. When I plugged in P0172 in this mbworld.org forum search engine, I was indirectly pointed back to this page. I then read each line, by line, and over again. I had missed the cracked PCV hose issue altogether!
This may be in another post, but the PCV hose part number has been updated from A203-018-12-82 to 271-018-12-82. My price August 29, 2008 was $14.24 plus CA sales tax from Mercedes Benz of Sacramento.
After many cleanings of the MAF, I have gotten very proficient in removing the air box. Takes only about 5 minutes now. The lower intake connection now has a hose clamp with a thumbscrew, I can untwist this connection with my fingers. The hardest part is reassembly when getting the air box tube back into the rubber hose. I use a little spray lube to allow the parts to slide together easier. Do not use silicone spray, it is supposed to be bad for the O2 sensors.
Along the way, I also had put in many bottles of Chevron Techron in the gas, changed the spark plugs with the magic hope of not seeing the CEL and fixing the now very lumpy idle.
The hose was purchased and I replaced it. The old one had a crack in the middle of the hose, not near the ends where the hose clamps are placed. There is not an easy way to describe the replacement, the hose slips on to the attachment nipples very easily. But the securing or tightening of the lower hose clamp is extremely tedious and is a real b!tch! Sorry, the stock clamp is a spring clamp that the MBZ techs must have a special set of pliers to remove and replace. For the home want a be fixer, I chose the basic screw on clamp (as suggested by the other post). If you can substitute the screw on with a spring clamp and have the a special tool, this is the way to do it.
Here are some pictures of the hose. Even after removing and replacing the air box, I was not looking for the cracked hose, but it is very obvious. I tore off the flap on the hose so you can see the large split. The lower hose clamp is the bear of the task.
2 cents - All of the info found on the web was good, but you have to be open minded to really figure out what the problem could be. At home, I don't have the proper equipment to truly test all parts. All in all, with the replacement the hose, plugs, MAF and the use of Techron. The car seems to run very smooth now. Power in the mid-band seems to come back alive.
Thanks,
-rob
Researching the web is good and bad when trying to diagnose car problems. One symptom can be related to many parts and each person's interpretation can be slightly different. When the idle first a little lumpy, I was able to spray copious amounts of CRC MAF cleaner on the MAF. First, just thru the metal mesh with the air cleaner removed and then the big plunge of removing he airbox with MAF. When the idle seem to improve slightly and then go back, I was sure that I needed a new MAF, from which I did order from the Arizona parts house. I go the Siemens unit for $276.
Next, this was not the main problem, I no longer saw the misfire code, but now the P0172 OBDII CEL code. I remembered this link:
https://mbworld.org/forums/showthrea...&highlight=pcv
I had not really paid much attention to the overall content, only that the description on how to remove the air box was very good. When I plugged in P0172 in this mbworld.org forum search engine, I was indirectly pointed back to this page. I then read each line, by line, and over again. I had missed the cracked PCV hose issue altogether!
This may be in another post, but the PCV hose part number has been updated from A203-018-12-82 to 271-018-12-82. My price August 29, 2008 was $14.24 plus CA sales tax from Mercedes Benz of Sacramento.
After many cleanings of the MAF, I have gotten very proficient in removing the air box. Takes only about 5 minutes now. The lower intake connection now has a hose clamp with a thumbscrew, I can untwist this connection with my fingers. The hardest part is reassembly when getting the air box tube back into the rubber hose. I use a little spray lube to allow the parts to slide together easier. Do not use silicone spray, it is supposed to be bad for the O2 sensors.
Along the way, I also had put in many bottles of Chevron Techron in the gas, changed the spark plugs with the magic hope of not seeing the CEL and fixing the now very lumpy idle.
The hose was purchased and I replaced it. The old one had a crack in the middle of the hose, not near the ends where the hose clamps are placed. There is not an easy way to describe the replacement, the hose slips on to the attachment nipples very easily. But the securing or tightening of the lower hose clamp is extremely tedious and is a real b!tch! Sorry, the stock clamp is a spring clamp that the MBZ techs must have a special set of pliers to remove and replace. For the home want a be fixer, I chose the basic screw on clamp (as suggested by the other post). If you can substitute the screw on with a spring clamp and have the a special tool, this is the way to do it.
Here are some pictures of the hose. Even after removing and replacing the air box, I was not looking for the cracked hose, but it is very obvious. I tore off the flap on the hose so you can see the large split. The lower hose clamp is the bear of the task.
2 cents - All of the info found on the web was good, but you have to be open minded to really figure out what the problem could be. At home, I don't have the proper equipment to truly test all parts. All in all, with the replacement the hose, plugs, MAF and the use of Techron. The car seems to run very smooth now. Power in the mid-band seems to come back alive.
Thanks,
-rob
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MBWorld Fanatic!
Joined: Sep 2011
Posts: 1,657
Likes: 35
From: Austin, TX
2005 C230K(sold), Mk7 Jetta
What engine do you have - M271? So you only have the vibration with AC on? Did you check the alternator pulley, it should freewheel in one direction. If it's solid both ways, that may be the source of vibrations.
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Junior Member
Joined: Feb 2015
Posts: 35
Likes: 6
W203 c180 2007
Rough idle
Yes its m271 and the when gear in D and AC on while idle vibration 100%.
If u move everything is fine
The vibration in air filter side.and u can feel it in break pedal.
If u turn off the AC and put gear in P . The vibration like 30% .and feel like its normal.
Please help me
If u move everything is fine
The vibration in air filter side.and u can feel it in break pedal.
If u turn off the AC and put gear in P . The vibration like 30% .and feel like its normal.
Please help me
Junior Member
Joined: Feb 2015
Posts: 35
Likes: 6
W203 c180 2007
My car c180 kompressor 2007
MBWorld Fanatic!
Joined: Sep 2011
Posts: 1,657
Likes: 35
From: Austin, TX
2005 C230K(sold), Mk7 Jetta
Def sounds like the alternator pulley. It will also make chirping sounds from the belt if you turn on the ac and put the car into reverse.
Depending on your car's mileage you can either replace the pulley, or the whole alternator.
See this DIY:
https://mbworld.org/forums/c-class-w...ditioning.html
UPD: if it's chirping in reverse, I'd suggest that you not use the ac until it's done, otherwise you are risking to break the AC compressor pulley, which will cost you a new ac compressor...
Depending on your car's mileage you can either replace the pulley, or the whole alternator.
See this DIY:
https://mbworld.org/forums/c-class-w...ditioning.html
UPD: if it's chirping in reverse, I'd suggest that you not use the ac until it's done, otherwise you are risking to break the AC compressor pulley, which will cost you a new ac compressor...
Last edited by VVF; Mar 8, 2015 at 06:30 PM.
