Checking old posts everything eems to point to this being a MAF problem. 2 questions: 1.) where is the MAF located and 2.) is it a DIY replacement? Any words of wisdom would be appreciated.

 

yes its a DIY job you need to pull the engine cover out and it just sitts in the end of the engine on the middle its roundish component with a5 pin connector........fault codes dont always led to air mass are gettin a falt spot like a hestitation on full throttle or not if you are than its air mass...........

 

Yes. DIY.
Can sometimes get away with cleaning rather than replacing (quite expensive) the MAF.
Use only genuine Bosch/MB MAF sensor.
Excellent DIY guide posted by Bazzle on this subject within the last 6 months.
MAF is located in different positions on different engine installations.
However it is located somewhere in the air inlet system before the throttle butterfly valve. Black plastic moulding clipped into air inlet tubing with a 5 pin (not always 5 wire) connector.

Stuart

 

Okay, so I'm headed to the stealership tomorrow and want to know what I should expect and perhaps how to push back on them if needed. I'm guessing they'll assume the MAF will need replacement since it's the easiest and most expensive way to fix the problem, right? The concern I have is the fact that there appears to be nothing wrong with the car other than the check engine light being on...no loss in power, no rough idle, no loss in fuel MPG, etc. Could it have been caused by "bad gas" and maybe just need to reset the code?

 

Yes it could be something other than the MAF but this would be unusual.
MAF is only one input into the fuelling system. The O2 sensors sense the fuel that has been added and burnt by the engine and create a signal that goes to the fuelling computer. If the O2 signal is wrong then the MAF may be required to make changes which take it out of range although not the cause of the problem. O2 sensors are often changed when there is nothing wrong them. However they do go wrong (usually due to contamination from poor fue)l. Easy to check O2 signal with the correct diagnosis equipment so before spending money on new O2 sensors (ensure correct MB genuine spares are used) by checkout the O2 sensor waveform. If this is OK then it is not the O2 sensors therefore 99.9% the MAF.

P0170/3 is Fuel Trim Malfunction which means the "computer" has past the permitted range of offset on the fuel trim adjustment. The fuel trim is altered many times a second and is centered +/- 30% around zero. The average of these readings is taken every so often and converted into an "offset" which is applied when the engine is started. Once again this offset is limited to +/- 30. Once this limit has been reached the system can't adjust adequate and a fault is signalled by 0170/3.

IF you are really concerned about spending your money unwisely reset the computer (need OBD scanner. Free service at some garages) and see how long it takes for the same codes to come back. IF you drive somewhat reservedly you may find the code / CEL doesn't come back until the moment you request snap power for overtaking etc. This is because the more "violent" (i.e. change rate) the engine fuelling requirements the more likely the system will go out of range unless well centered within range.

Cleaning MAF MAY resolve your problem but this doesn't always work and even when it does it tends to extend life by altering the offset say by 10% rather than resetting it back to where it should be when new = 0.

The CEL often detects problems long before symptoms become obvious to the driver. The CEL feature is a requirement of emmissions legislation. If the CEL is ON or does not come on during startup procedure the vehicle will fail its annual emmissions test either because the CEL system isn't working as required AND/OR because of the underlying...possibly unnoticed to the driver...fault.