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2002 SLK, 2008 C300, 2010 ML350
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117 Posts
Discussion Starter #1
Ok, I have written about a poor idle and now finally I get a code. P0172-System Running Rich. Bank 1

So where should I start? :confused:
 

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Premium Member
1998 SLK 230 Kompressor, 1993 500 SEC
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109 Posts
Is that after driving, or lots of idling trying to work out what the issue was?
 

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Moderator
1998 SLK 230
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2,648 Posts
System Too Rich

What does this mean?

OBD Code P0172refers to
Basically this means that an oxygen sensor in bank 1 detected a rich condition (too little oxygen in the exhaust). On V6/V8/V10 engines, Bank 1 is the side of the engine that has cylinder #1. Note: This DTC is very similar to P0175, and in fact your vehicle may show both codes at the same time.

Symptoms

Possible sumptoms of OBD code P0172
You will more than likely not notice any drivability problems, although there may be symptoms such as a misfire.

Causes

Possible causes of OBD code P0172
The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters can cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry. There could be a vacuum leak. There could be a fuel pressure or delivery problem

Possible Solutions

Inspect all vacuum and PCV hoses, replace if necessary Cleanthe MAF sensor. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling Inspect fuel lines for cracks, leaks, or pinches Check the fuel pressure at the fuel rail Check the fuel injectors, they may be dirty. Use fuel injector cleaner or get them professionally cleaned/replaced. Check for an exhaust leak before the first oxygen sensor (this is unlikely to cause the problem, but it is possible)
 

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1998 SLK 230
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2,648 Posts
unplug the MAF and start the car. it will throw another code, but the car will now not use the MAF to do air fuel in real time rather off a fail safe hardcoded table off the ecu. if it still not smooth its probably unmetered air getting in past the MAF check all vac lines
 

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2002 SLK, 2008 C300, 2010 ML350
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117 Posts
Discussion Starter #5
Subby, I did everything you said to do and still had the code. So the only thing I thought of was when I changed the MAF out I also replaced the spark plugs. No reason, just figured it was time. I decided to pull one of the plug and sure enough it smelled like gas. So I actually dug the old plugs out of the trash, cleaned them off, checked the gaps, and put them back in. I then disconnected the battery to reset the computer. And sure as shit, the car runs beautifully! No codes, good emissions. I am so friggin' happy.

Just to let others know, I re-installed the NGK IFR 6D10 plugs. the new plugs which are obviously wrong are Bosch FR71133X (6360 iridium) which I was told was compatible with my car.

Oh well, live and learn. Thank you both for the help.
 
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