w203 (cl203) maf sensor problems

[nick9955]

hi new to this forum but I have a problem that isn't a big issue but don't want to keep throwing money at it.

I have a cl203 2005 with the m172 engine 180 k

so I had this problem where whenever I started the car the rpms will be very high (1.5k) for a second then slowly drop to normal but it will jump around a little, then if I put it in drive or reverse the rpm will jump around like crazy between 0.5k and 1.5k will drive fine at speed no hesitation or poor mpg etc. but if I ever come to a stop in the journey the jumping comes back until I start moving again, also I had an intermittent code for the maf sensor and for too rich or too lean mixture.

since then I have replaced the maf sensor, this has fixed the problem almost completely.

on cold start it will still rev high and jump a little when selecting reverse or drive. when warm all of this is gone.

The problem is I have is a constant engine management light for maf sensor which will go away if i erase the code (it won't come back in that drive) but whenever i turn the car off and on again the code always comes back and its always for the maf only.

any idea why the light still comes on? it is running so much better than before and not throwing codes for mixture anymore either, but the constant light is so annoying.

 

[BlackC55]

Was the MAF a genuine one? Cheap copies just don't work properly.

I would expect you have an air leak, or oil in the wiring loom. What does the live values say for the MAF? Have you tested the wiring also?

 

[BlackC55]

BTW the MAF's on this engine are usually very very reliable. They only usually fail due to oil contamination from the loom or the intake.

 

[nick9955]

hi thanks yes it was a maf from ebay, and I don't know how to check the live values i also only have a cheap obd2 scanner.

I think in that case I will put the old one back in.

have checked for an air leak but didn't find anything, I haven't checked the wiring loom, but when I took the maf off the the bottom of the intake pipe where it attaches to the supercharger seemed more oily than normal, and around the vacuum line that goes to the valve cover was a little oily.

I think I will put the original maf back on and then clean it with some maf cleaner later.

 

[nick9955]

if there is oil in the wiring loom which is what I suspect is more likely in my case than the air leak, what is the solution?

 

[nick9955]

so was just putting the old maf back in and will show some pictures of maf and oil on intake etc

 

[nick9955]

after comparing them, original seems to have a resistor type thing missing? the 1st image is the original 2nd is ebay maf

 

[BlackC55]

if there is oil in the wiring loom which is what I suspect is more likely in my case than the air leak, what is the solution?

eBay cheap MAF's don't work. Get the real thing. There is a pipe that leaks on this engine giving maf codes. Its been covered on here many times. You have to take the air box off to see it.

A new loom, cam magnet, blocker loom and what ever component has been contaminated.
It maybe best to get it diagnosed properly by a MB specialist. This will save time and money if their diagnosis is accurate.

 

[nick9955]

eBay cheap MAF's don't work. Get the real thing. There is a pipe that leaks on this engine giving maf codes. Its been covered on here many times. You have to take the air box off to see it.

A new loom, cam magnet, blocker loom and what ever component has been contaminated.
It maybe best to get it diagnosed properly by a MB specialist. This will save time and money if their diagnosis is accurate.

Yes its the "$15 fix" This is fine on my car, could be the wiring problem which is annoying. any idea about why that part is missing on the old maf?

 

[BlackC55]

Its probably a copy one too. What make is it?

 

[nick9955]

Its probably a copy one too. What make is it?

it's the original mercedes part it was a siemens part I believe