So I have a 2004 C230 Kompressor.

Recently, I noticed a lag and choke (Sorta like it was misfiring) during acceleration.

At first I thought maybe it needed new spark plugs, or clean fuel injectors. No check engine light, so I was confused.

I decided to take it to the shop, and there they scanned it but my computer didn't notify the system of any error logs!

This is what the tech told me: "This week we've had 5 Mercedes brought in, with the same symptoms your car is having. Some were so bad, the car would jerk hard! Each time, it turned out to be the Mass Airflow Sensor. The problem is the MAS regulates the amount of fuel and air to drive the car. When the sensor is bad, it creates an inbalance in the flow and makes your car jerk. By giving it more gas, it feeds it more fuel, and you'll notice the jerking kinda goes away."

"Ok so why isn't my computer detecting a problem?"

"Well, your computer registers what is called a Key Cycle. The computer runs a self check each time you turn on the car. And while we know that the sensor is bad, your computer hasn't detected it yet because it doesn't "see" it as a problem yet. Give it about 40 more Key Cycles (starts) and the Check Engine light will come on, that's when you know your computer has detected it."

"Will driving it around like this hurt the car?"

"Not at all, it won't leave you on the side of the road, or hurt / damage the vehicle."

Today, the light finally came on after driving it for about 2 weeks sinceI took it to the shop. And the repairs came out to about 600something bucks. **ouch**

I figured this might help some of you out. I thought it was helpful.

 

Hi,

Your mechanics analysis is "spot on"! Mileage 50 - 70k?

During the key "startup" checks (similar to your PC "booting") the resistance of the MAF "hot film sensor" is measured before the motor is running.

As the resistance of the MAF changes with age (possiblt due to dirt / contamination) it causes the EMS Engine Management system to apply an "offset" to the fueling map which impacts the LTFT Long Term Fuel Trim. Once this reaches a predetermined level it triggers the CEL Check Engine Light.

Sometimes this "out of range" problem can be addressed by cleaning the MAF but this doesn't always work and is not recommended by MB since it doesn't give QA Quality Assurred results.

Hot Film sensors do not include a "cleaning cycle" unlike the old (less reliable) "Hot Wire" sensors which used to burn off any contamination.

600 USD isn't a surprise. Majority of this is parts cost. You can pick them up on eBay at a good rate. I advise only using genuine new Bosch sensors which sometimes appear but there is of course the possibility of used and non Bosch parts being sold as "Genuine" / "New". Unless you know what to look for you can easily be duped.

 

rastabenz,

Recently I had similar problems with my SL500/113engine and before replacing the MAF sensor tried using a new product from CRC which I now recommend. As a practical matter, $5.99 invested in a cleaner for this sensor beats $500 for a new one, as long as the sensor wires are intact. This link will take you to the CRC site for a write up on the product.
http://www.crcindustries.com/auto/co...=05110&S=N

If you decide to try this approach, I highly recommend changing your engine air filter first, then explicitly follow the directions on the can of cleaner to clean the MAF Sensor.

After cleaning, as snanceki points out, your revitalized sensor will now transmit new information to the ECU which will cause it to 'relearn and reset' fuel/air values...give it a few starts to work properly and I think you'll be pleased.

If you do end up replacing the sensor, snanceki is absolutely right about Bosch only-

Bob

 

Thanks guys <3