wallra

02 C240 keeps setting misfire codes for cylinder #2,#4. replaced mass airflow sensor with dealer part had it adpted by the dealer for the new mass sensor. tried swaping coils and wires with other cylinders,same thing.Only happens when you drive the car hard (wide open throttle)from take off.When it happens it will Idle rough,then shut it off and restart and it runs smooth until you take off hard agin.

Glyn M Ruck

What do you mean by replaced MAF "had it adapted by the dealer"?.

What happens if you unplug the MAF and drive the car on a default map?

It could still have a MAF playing up - it can make the engine run lean at high rpm and cause misfires but not sufficiently to trigger a fuel trim code if the misfires only happen at wide open throttle when the O2 sensors are not in the loop. Also check your air and fuel filter. Fuel related problems like dirty injectors, weak fuel pump, clogged fuel filter can cause misfires. I presume your plugs are OK?? Run a few tanks of gas with Techron concentrate if you suspect injectors

wallra

yes I replaced the maf sensor,and had it adapt at the dealer. I will try running it with the maf unplug and also put fuel pressure gages on it to see what the pressure is when the problem happens.I replaced the plugs,fuel & air filters.

Glyn M Ruck

What do you mean by "adapt" - modified? changed? adjusted? revised? fitted?

Sorry - I just don't understand you.

wallra

adaptation,this tells the computer to recognize the new part

Glyn M Ruck

OK thanks - sorry I did not understand let me know how it runs with MAF unplugged

wallra

got it fixed. ended up having to have the dealer do an adaptation on all the sensors for the engine.They told me that I had a bad maf,and even though I replaced it and did an adaptation on that,the rest of the sensor went out of spec and the crank sensor was'nt reading right because it needed to be reset this is what was making the engine misfire.I guess I need to invest in a mercedes star scan tool to be able to do the adaptation resets.

Glyn M Ruck

A STAR diagnostic machine will cost you more than your car is worth but a good OBDII/CAN scanner from Harbor Freight or Kragens is a great help.

Pleased your car is fixed

krisv420

Got mine at kragens for 70 dollars i believe. Lets just say i could have paid 1XXX$ to fix my car when i had miss fire codes. Good thing i bought a OBDII reader. And spent like 300 in parts and fixed it myself. "Thanks to a lot of NICE members here" aka only some.

But i have seen Star diag systems on ebay for 2500 with a laptop.

PA_Pete

I've never heard of this before. So if I order up a MAF sensor myself and put it on the car myself, your saying that it won't work because I need to have the Star Diag System "adapt" it to the car?

Glyn M Ruck

Pete, MAFs are plug & play you might notice my question above. I think we have a translation issue

Glyn M Ruck

Kris, thanks for coming in with your experience. A STAR for $2500. That's a hell of a good price I understand!

PA_Pete

Okay, that's what I had thought, being that they were always that way on all of the other cars I owned. I was mainly asking because I will probably need one. So the dealership tells me. I'm also getting a CEL, but before I pay mucho money for another MAF sensor, I'm going to take out the existing one and give it a good cleaning. CRC I believe, makes a special cleaner just for MAF sensors, it's worth a shot I figure, the worse I could do is break it, which it may already be.

Glyn M Ruck

Pete - give it a good clean first - you may be pleasantly surprised. Also beware of buying MAFs on the internet. Their are some sharks out there selling VW ones that fit the Benz but won't calibrate.

PA_Pete

REALLY?! Wow, good to know, Thanks a lot for giving me that heads up! If I were to buy one from the internet, which brand or make of MAF should I go with? Is there a way to tell without hooking it up to the car whether or not it is for a MB or a VW?

Glyn M Ruck

Pete - you are going to have to ask an American member that question - I would only use genuine Bosch. From all I've read you can't externally distinguish the VW unit from the MB unit - I'm sure there must be a number or something but I have not found it in print - only warnings and many people that have had the problem - including a friend of mine!

Glyn M Ruck

Some more on this term "adaption" after doing some reading. It seems to be used by Bosch. Definitely a translation issue

Anyway - in this context. If the car throws a code & you change the MAF - (you need to "adapt it" - ie cancel the code) - This allows the ECU to get the fuel trim correct more quickly. If you dont cancel (adapt) the code it takes about 3 restarts to get the STFT & LTFT correctly calibrated - So it is plug & play but if you don't cancel the code it just takes a little longer for the ECU to get the fuel trim calibrated.

BTW - The Bosch part number is stamped on the black plastic sensor cover of the MAF - any numbers on the main body of the MAF are just manufacturing codes. It's the sensors that vary.

billbugger

So then, instead of getting it 'adapted' couldn't you just start the car, let run a minute, turn it off. Lather-rinse-repeat 3 times?

Glyn M Ruck

Yes, precisely! - might take a little longer than that - 3 short drives or extra rinse & scratch your butt - but that's my understanding. The dealers would rather you take it to them so they try to complicate issues.

wallra

I have a snap on modis scan tool it's great for reading codes but can't do the adaptation for mercedes with it.great tool for vw and japanese cars also american.I'm going to buy the after market star tool,just not the one made in china.The mercedes mechanic told me you have to be careful with the aftermarket scan tools you can do more harm than good.I'm a mechanic with my own shop with 26 years in the field. I don't work on a lot of mercedes thats why I was on here asking Question. sometime looking on these fourms can point you in the right direction.

Glyn M Ruck

Hi - your use of the word "adaption" keeps confusing us all but I know what you mean

A decent aftermarket scanner is fine for reading & cancelling codes, reading live data (the better ones) & resetting the service indicator.

For any other work on a Benz such as selecting Bi Zenon headlights = present etc. you need a STAR and even that can't do everything. - you need a modified developers DAS to do certain reprogramming.

Feel free to ask questions on the forum - the good folk here are vey helpful & collectively have a lot of experience.

Glyn M Ruck

BTW - watch the CPS (crank position sensor) they often fail and cause all sorts of problems as you can imagine if the engine does not know when it's at TDC

wallra

yeah the crank sensor was what ended up making this thing skip.The tech at mercedes told me that was what he had to do the adaptation on and he needed to drive down the road to set it at different RPM'S and speeds to reset it.The car was running like it was hitting the rev limiter.that why it was skipping the comuter lost it's settings and it would shut the fuel off at 5200 RPM.He told me sometimes when you plug after market scanners into the cars and clear codes you end up wiping the programs out.I changed lots of MAF sensors on mercedes and this is the first one to do this to me.I've resat lots of codes in the past and never seen this befor.Thanks for your help!

wallra

Adaption, is a program you can go into and reset all the base settings on all the sensors. a good shop scan tool like the snapon modis can do this.I'm able to do it on pre 2000 merecedes. after 2000 mercedes change the software so after market shop can't access. the mercedes scan tool cost 22,000, but their is some after market star scan tools that work the same they just don't have the touch screen software.

enap66

Hi,

I too replaced the MAF. I took it to benz, they quoted me a lot, so I bought the tools and the MAF on ebay and popped it in. I bought a cheap one on the net, probably a fake cause the car still doesn't run correctly. In fact, I had put the MAF in, after which, the CEL came on, whereas before installation, the CEL wasn't on, but it WAS running poorly, just without the CEL light. (from not having enough air it seemed.) In other words, the car ran the same after I put the MAF in, only the CEL came on as well a week after installation. Weird, right? So I'm figuring it was a fake. So tomorrow I'm going to clean the old one (I happened to keep it since it looked perfect.) and pop it back in. About this "adapting" or "reseting" I guess... I stopped by a mechanic, he said that's malarkey and that you don't need to reset it, it'll be fine without, as long as you put in a genuine bosch. If you don't though, one may have problems, which may be the reason why I'm having problems???? Anyway, 2 questions:

1. I bought my MAF on ebay. Not only did it NOT work but the CEL came on AFTER installation. Why? Is it fake do you think?

2. What's this about reseting or adapting? If I clean the old one, properly put it in, shouldn't it run fine?

Thanks all! I do appreciate the help, sincerely!!!