mleskovar

Yes, if that's the problem to begin with. Be sure to clear the CEL. The MAF relies on the metal surface to function properly. If the wires become dirty/oily it won't sense the air flow right. I understand some MAFs are given an extra shot of electricity to heat it beyond normal every time it's cycled to clean it off. Look at it under a magnifying glass for contamination.

Glyn M Ruck

It all depend on whether your old MAF is OK - If so it will respond to cleaning.

Half the MAFs on the internet that fit are for VW/Audi & won't work on the Benz. Make sure you get a genuine Bosch with the correct part number displayed on the black plastic sensor cover.

First thing to do is to unplug the MAF and see how the car drives. This forces the ECU onto a default MAP - not perfect mixture control but the car should run fine.

I would fit a new, genuine Bosch MAF with the correct part number from a reliable source & be done with it. You are just delaying the inevitable & wasting money in the process.

enap66

Thanks all, I will try cleaning it first, then installing it again, if it's still bad, buy another. Oi....

Glyn M Ruck

Yeah - do that. I know it's expensive but you can't go on driving with a MAF that is misbehaving - Good luck!

enap66

I cleaned the old MAF and put it back in. So far, no go. I guess I need a new one. I'll buy a Bosch made MAF and hope for the best. I just don't want to buy a new one and still be having this problem. I'm sure it's the MAF, my code machine is telling me so and the symptoms are textbook MAF problems so... Anyway, I'm just thinking, "could it be the wires that lead into the MAF, the connector wires? Are they corroded?" I tried spraying those too with the MAF cleaner, it dries very fast so I don't think it's going to hurt them but still, nothing. Can you recommend any other places to clean on there that are linked to the MAF or... Otherwise, I'll just have to buy a new MAF from Bosch.

Glyn M Ruck

Wiring on the car other than HT wires does not give trouble. The V6 models don't have the oil in harness problems that the I4 suffers from leaking cam sensors.

The only other thing you can clean is the throttle body but it won't fix your CEL. A proper new Benz MAF will.

enap66

I'll let you know how it works out. I'll probably do it in a week or two. Car still runs, just not perfect so it can wait a bit longer.

Thanks for all your help!

Glyn M Ruck

enap - I just reread the thread because it's on multiple vehicles. What codes are you getting? - We have all just assumed you are getting a MAF code is this so? What mileage has the car done? what are the driveability problems you are experiencing? Give us those codes.

It could be SP wires, coils, fuel pressure, fuel filter clogged, plugs, dirty throttle body etc.etc. etc

enap66

After some time of the CEL being on, I finally made the leap and bought a new O2 sensor. It is the upstream, driver's side O2. I installed it luckily with no problems in about 10 minutes and started her up, anxious to see if the CEL had gone off but NOPE, it's still on. Someone told me I have to take it to pepboys or somewhere to have the CEL taken off by their code reset machine but what I don't understand is 1. sometimes the code would go off for an hour or two and then return so if the problem is fixed, shouldn't it just go off as it did in the past?
2. what will these guys charge just to turn it off?

Also, I need a new battery. I've heard that sometimes by replacing the battery (or removing the cables for 10 min.) resets the CEL? Any suggestions?

Oh and one more thing... I replaced the air filters with those cheesy ones at the local auto shops, u know, the ones that don't fit properly? Anyway, should I get a new one on autohauz and if I do so, as long as it fits properly, could it help with the codes possibly? Perhaps that's what is knocking the codes off? I don't think so but you never know!

Thanks!!!!

Glyn M Ruck

P0172 = System too Rich (Bank 1)
P0175 = System too Rich (Bank 2)

Why did you only replace one upstream O2 sensor & not both?
If the fuel trim comes right then the CEL will extinguish after some miles of use - or you can cancel with an OBDII scanner.

Unless the air filter is clogged it won't cause this but I recommend getting a decent set of filters.

enap66

Guys, can you give me an idea of what air filters to purchase? I found some for a good price, with this part number:

1120940604

I think these are the OEM but would like to check with you all before I waste $25 bucks. It's a 2004 C240.

Thanks!

enap66

Are you saying that P0172 and P0175 point to BOTH upstream O2 sensors being bad and that I should have replaced both the driver's side and passenger's as well? The codes were pointing toward driver's side only, or so I thought?

Thanks....

MIKESV8

why not put in k&n's? i had a question too, how do you get to the MAF? is there a DIY about it? if so, i'd appreciate it if someone posted it on here because i can't find it. i'd like to take a look at mine and see how dirty it is if it's not a large task.

Glyn M Ruck

If you are getting both codes then both banks need replacing.