Driving w/out Mass Air Flow Sensor connected?? - Mercedes-Benz Forum
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#1 (permalink) Old 08-20-2009, 10:59 PM
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Post Driving w/out Mass Air Flow Sensor connected??

The Mass Air Flow Sensor in my 2000 E320 wagon(2WD) has gone bad for the second time in 6 months. The first replacement i bought was a rebuilt unit. I have now purchased a brand new BOSH online, but it will not be here until next week.

Shcucks tells me i can disconnect the electric connector on the Mass airflow sensor and the car will run in a default mode until i get the new one. I had to do this for about 10 miles today and it did run with no issues except the check engine light came on.

Do you agree that i can drive with the Mass Air Flow Sensor in the car, but without the electrical connector hooked up? Can i drive 500 miles like this without ruining anything more on the car until i get the new one?
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#2 (permalink) Old 08-20-2009, 11:42 PM
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Definitely not. Even if a mass airflow sensor is "bad" it is still measuring the airflow into the engine, just not as precise as the emission control system would like.

I wouldn't drive or run the engine with an important part like that missing. Keep it hooked up. You will cause more harm than good disconnecting it.

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#3 (permalink) Old 08-21-2009, 12:12 AM
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ThankS! That;s what my wife said too. She's the one who is usually reading on this forum.
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#4 (permalink) Old 08-21-2009, 09:10 AM
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The truth is, that nobody actually knows what is default mode on our cars.
I drove Jetta TDI without working MAF for over 1000 miles, but the car had to CAT.
So with gas engine I would suspect that lack of MAF will trigger more misfires and possibly cook up the cats.
Again, this is just guess since we just don't know. I wonder if dealer might give more educated answer?
Than consider that the engines worked without MAFs for over 100 years even with lousy carburetors.
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#5 (permalink) Old 08-21-2009, 09:17 AM
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I agreed with KT1, and I think it may do not do much damage if you will change it within 100miles

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#6 (permalink) Old 08-21-2009, 11:14 AM
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What follows is JMHO...

Disconnecting the MAF (or really any other sensor) can be useful as a diagnostic tool. Driving with it disconnected beyond testing is simply asking for trouble, spelled $$$$.

In other words, can you and should you are two very different questions.

But considering that driving very long with a bad MAF will shorten the life of your O2 sensors and CATs (all of which can be rather expensive, many times the cost of buying the MAF even at the stealer) it seems to me rather foolish to take the chance of driving with the MAF disconnected.

Reasonable conclusion: if you must drive the car with a bad MAF ... don't. Rent a car or pay more for the MAF locally, but once it's bad -- and particularly so when it's bad enough that the car runs better with it disconnected -- don't drive it unless you're racing to the ER with your loved one facing possible death. In other words, it's a true emergency.

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#7 (permalink) Old 08-21-2009, 11:23 AM
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Thank you Greg, I will take your advise.

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#8 (permalink) Old 08-21-2009, 12:40 PM
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Greg has valid points, but than we are still kept in the dark what our cars have in their programs. How many of us know that the computer will turn the engine off when it reaches the danger temperatures?
Frankly I am not even sure about it. An owner of ML320 reported that feature, so I assume since W210 is a sibling we have it as well, but never had a need to test it.
The point I am getting to is that our cars have well developed protection from the owners. So to my understanding if driving with MAF disconnected would be harmful -the computer would not allow it.
To be sure about it I would call MBUSA, although I found on more than one occasion that I know more about the car than their experts do.
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#9 (permalink) Old 08-21-2009, 01:32 PM
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Hmm. I always thought if you shut off an overheated engine it could lock it up because you stop the flow of coolant and the fan briefly causing a temperature surge.

I've heard its best to keep a hot engine running at slightly above idle speed to increase the water pump flow and fan speed. Of course this is assuming the engine hasn't completely lost its coolant.

Also I've heard to run the heater full blast. But this could be an old wives tale though.

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#10 (permalink) Old 08-21-2009, 01:42 PM
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It is old wives tale on Mercedes, although it still applies to most of other brands.
As you can read in parallel topic -MB are equipped with electric recirculating pump, that circulate the coolant few minutes after engine off.
Than it is still better to shut off overheating engine, than letting it melt.
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