I've been posting intermittently about a problem starting my 2001 E320 lately. I've finally narrowed it down to my maf. I purchased the maf on ebay and it was sufficient to solve my fuel trim problems, but caused another. It seems the MAF is causing the car to die upon startup.

When starting the car, if I put the key in and immediately start the car, the engine fires up and suddenly dies (curiously, if I turn the key to the on position and wait a few seconds before starting the car, it starts fine). through various experiments I tried, I thought I had narrowed it down to possibly a bad battery, alternator, fuel pump, spark plugs, cps, and various other things. I then remembered what had happened the time I had disconnected the (old) maf and forgotten to reconnect it.

When the car gets no info from the maf, the car will spin the fan faster and faster and faster until you can feel a strong warm breeze coming in off the engine block. In addition, the car will go into limp home mode until you reconnect the maf and restart (i've never tried plugging the maf back in while the car was still running).

So, curious, I disconnected the MAF. with the MAF disconnected, the car starts without hesitation every time. I've already spoken to the vendor who sold me the maf, and they are going to send me a replacement. I just wanted to post this as a heads up in case anyone else has this problem in the future. With the failure I was getting I did not get any of the usual p0173 or p0170 fuel trim codes. Hopefully the replacement maf I receive will not have the same problem.

Another problem I'm having which may or may not be related, is the car doesn't seem to have the power it once did. I've recently changed the plugs in the car for bosch platinum 2s, so I don't know if it might be the plugs. I'm going to pug OE plugs back in and see if that makes a difference.

The last problem is somewhat alarming. there will be times when I might let off the gas briefly, then try to pass a car, or just *go*. when I do that, intermittently the car will surge oddly, like I'm pumping the gas pedal. a few seconds later the surging stops, but this could make for a dangerous situation on the highway (for example) if I need passing power I think is there and it's unexpectedly gone. anyone have any ideas on that?

 

Sounds like this is also the MAF sensor as its unable to adjust the air/fuel ratio because it cant tell how much air is entering, i wouldnt bother swapping your plugs back round, try the new MAF first.

 

update: I just spoke to the vendor of the MAF, and they were convinced that my problem was related to anything but the MAF. They seemed very loathe to RMA the MAF I'd purchased, citing possible battery problems, vacuum leak, fuel delivery, and other possible issues. My concern is that if I disconnect the MAF the car starts without hesitation. Their answer is that maybe there's a grounding problem with the circuit that is open when the maf is connected that's not there when the MAF is unplugged. Is there anyone in the Austin area who would be willing to lend me 5 minutes of time on monday or tuesday to see if their stock MAF has the same effect on my car as my suspect MAF? call me cheap, but I don't want to pay $100 to a mechanic to tell me what I already think I know is wrong.

 

So, you are saying that the company that you bought the MAF from is refusing to send out a new MAF? HOw long have you been working on Mercedes? Because it seems to me that you have gone through all the checks and tests necessary to condemn the MAF. Like checking voltage and ground at the MAF plug, and resetting all the mixture adaptations and relearning the throttle valve stop when you put the new MAF in. Now, you have two options. Talk to the company about getting a new MAF so that you can try it and findout that its not going to fix the car because the MAF that you have is probably o.k. Or take it in to someone who can #1 pull codes for you, #2 check the voltage and ground of the MAF, #3 make sure it isn't another problem.#4 Give you an estimate on what its going to cost to fix it.

My beef is with people who seem to want to own a benz but never pay for it to be serviced properly. You dont have the experience or the knowledge to diagnose this car so dont say that you "think" you already figured out what is wrong. I'm not saying that you have to take your car in and get raped by the dealership, but let me put it in perspective for you..................Your right arm starts to feel numb at times and you lose all control of it on occassion. You are told that they have to operate and repair nerve and tissue damage. Would you .........(a)Shop around for the lowest priced doctor in the area to do the operation because your "cheap" ...............(b)ignore it because you "think" that you can fix it yourself ......................or (c) pay whatever it costs to fix your arm so you can be "cheap" with both arms working again?

I dont think 100 dollars is alot to pay to find out what is wrong with your car from a techinician that deals with this stuff everyday. And I think that it could be a number of things wrong with your car. I cant diagnose this perticular problem over the net because it has so many variables. Good luck with your guess.......I bet you play the lottery every friday also

 

Sorry to revive an old thread (I've been busy with work and haven't had time to post), but I purchased and installed a new MB branded maf and all of my problems magically disappeared. the acceleration is tight, the random engine surging when passing on the highway is gone, the car starts without dying every time, the car doesn't randomly start shuddering while driving on the highway. As for the company that sold me the defective maf, they're fortunately doing the right thing and refunding my money and accepting the defective part back.

 

I read more and more posts about people buying a faulty maf off of ebay....and not just for MB, but I think most use the same sensor. Don't know if it's the same vendor or what, but too many fail and cause big problems troubleshooting because people assume a new part is OK.

 

I have also seen this with cheap aftermarket MAF sensors. It seems some copies are made in China and do not work with a high enough accuracy. One other bizzare thing I have had cost me, is do not be tempted to swap MAF's between cars. God knows why, but despite the part nos being identical, neither of them worked afterwards, and I had to buy 2 new ones to resolve the problem. I worried that the defective car had blown them both up in some way, but new ones have now been OK for over a year now.